diff options
Diffstat (limited to 'src/org/apache/commons/lang3/ObjectUtils.java')
| -rw-r--r-- | src/org/apache/commons/lang3/ObjectUtils.java | 1216 |
1 files changed, 608 insertions, 608 deletions
diff --git a/src/org/apache/commons/lang3/ObjectUtils.java b/src/org/apache/commons/lang3/ObjectUtils.java index 69dde6f..a75184c 100644 --- a/src/org/apache/commons/lang3/ObjectUtils.java +++ b/src/org/apache/commons/lang3/ObjectUtils.java @@ -1,608 +1,608 @@ -/*
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.apache.commons.lang3;
-
-import java.io.Serializable;
-import java.lang.reflect.Array;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-import java.util.Collections;
-import java.util.Comparator;
-import java.util.HashMap;
-import java.util.Map;
-import java.util.TreeSet;
-
-import org.apache.commons.lang3.exception.CloneFailedException;
-import org.apache.commons.lang3.mutable.MutableInt;
-
-/**
- * <p>Operations on {@code Object}.</p>
- *
- * <p>This class tries to handle {@code null} input gracefully.
- * An exception will generally not be thrown for a {@code null} input.
- * Each method documents its behaviour in more detail.</p>
- *
- * <p>#ThreadSafe#</p>
- * @since 1.0
- * @version $Id: ObjectUtils.java 1153350 2011-08-03 05:29:21Z bayard $
- */
-//@Immutable
-public class ObjectUtils {
-
- /**
- * <p>Singleton used as a {@code null} placeholder where
- * {@code null} has another meaning.</p>
- *
- * <p>For example, in a {@code HashMap} the
- * {@link java.util.HashMap#get(java.lang.Object)} method returns
- * {@code null} if the {@code Map} contains {@code null} or if there
- * is no matching key. The {@code Null} placeholder can be used to
- * distinguish between these two cases.</p>
- *
- * <p>Another example is {@code Hashtable}, where {@code null}
- * cannot be stored.</p>
- *
- * <p>This instance is Serializable.</p>
- */
- public static final Null NULL = new Null();
-
- /**
- * <p>{@code ObjectUtils} instances should NOT be constructed in
- * standard programming. Instead, the static methods on the class should
- * be used, such as {@code ObjectUtils.defaultIfNull("a","b");}.</p>
- *
- * <p>This constructor is public to permit tools that require a JavaBean
- * instance to operate.</p>
- */
- public ObjectUtils() {
- super();
- }
-
- // Defaulting
- //-----------------------------------------------------------------------
- /**
- * <p>Returns a default value if the object passed is {@code null}.</p>
- *
- * <pre>
- * ObjectUtils.defaultIfNull(null, null) = null
- * ObjectUtils.defaultIfNull(null, "") = ""
- * ObjectUtils.defaultIfNull(null, "zz") = "zz"
- * ObjectUtils.defaultIfNull("abc", *) = "abc"
- * ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE
- * </pre>
- *
- * @param <T> the type of the object
- * @param object the {@code Object} to test, may be {@code null}
- * @param defaultValue the default value to return, may be {@code null}
- * @return {@code object} if it is not {@code null}, defaultValue otherwise
- */
- public static <T> T defaultIfNull(T object, T defaultValue) {
- return object != null ? object : defaultValue;
- }
-
- /**
- * <p>Returns the first value in the array which is not {@code null}.
- * If all the values are {@code null} or the array is {@code null}
- * or empty then {@code null} is returned.</p>
- *
- * <pre>
- * ObjectUtils.firstNonNull(null, null) = null
- * ObjectUtils.firstNonNull(null, "") = ""
- * ObjectUtils.firstNonNull(null, null, "") = ""
- * ObjectUtils.firstNonNull(null, "zz") = "zz"
- * ObjectUtils.firstNonNull("abc", *) = "abc"
- * ObjectUtils.firstNonNull(null, "xyz", *) = "xyz"
- * ObjectUtils.firstNonNull(Boolean.TRUE, *) = Boolean.TRUE
- * ObjectUtils.firstNonNull() = null
- * </pre>
- *
- * @param <T> the component type of the array
- * @param values the values to test, may be {@code null} or empty
- * @return the first value from {@code values} which is not {@code null},
- * or {@code null} if there are no non-null values
- * @since 3.0
- */
- public static <T> T firstNonNull(T... values) {
- if (values != null) {
- for (T val : values) {
- if (val != null) {
- return val;
- }
- }
- }
- return null;
- }
-
- // Null-safe equals/hashCode
- //-----------------------------------------------------------------------
- /**
- * <p>Compares two objects for equality, where either one or both
- * objects may be {@code null}.</p>
- *
- * <pre>
- * ObjectUtils.equals(null, null) = true
- * ObjectUtils.equals(null, "") = false
- * ObjectUtils.equals("", null) = false
- * ObjectUtils.equals("", "") = true
- * ObjectUtils.equals(Boolean.TRUE, null) = false
- * ObjectUtils.equals(Boolean.TRUE, "true") = false
- * ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true
- * ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false
- * </pre>
- *
- * @param object1 the first object, may be {@code null}
- * @param object2 the second object, may be {@code null}
- * @return {@code true} if the values of both objects are the same
- */
- public static boolean equals(Object object1, Object object2) {
- if (object1 == object2) {
- return true;
- }
- if ((object1 == null) || (object2 == null)) {
- return false;
- }
- return object1.equals(object2);
- }
-
- /**
- * <p>Compares two objects for inequality, where either one or both
- * objects may be {@code null}.</p>
- *
- * <pre>
- * ObjectUtils.notEqual(null, null) = false
- * ObjectUtils.notEqual(null, "") = true
- * ObjectUtils.notEqual("", null) = true
- * ObjectUtils.notEqual("", "") = false
- * ObjectUtils.notEqual(Boolean.TRUE, null) = true
- * ObjectUtils.notEqual(Boolean.TRUE, "true") = true
- * ObjectUtils.notEqual(Boolean.TRUE, Boolean.TRUE) = false
- * ObjectUtils.notEqual(Boolean.TRUE, Boolean.FALSE) = true
- * </pre>
- *
- * @param object1 the first object, may be {@code null}
- * @param object2 the second object, may be {@code null}
- * @return {@code false} if the values of both objects are the same
- */
- public static boolean notEqual(Object object1, Object object2) {
- return ObjectUtils.equals(object1, object2) == false;
- }
-
- /**
- * <p>Gets the hash code of an object returning zero when the
- * object is {@code null}.</p>
- *
- * <pre>
- * ObjectUtils.hashCode(null) = 0
- * ObjectUtils.hashCode(obj) = obj.hashCode()
- * </pre>
- *
- * @param obj the object to obtain the hash code of, may be {@code null}
- * @return the hash code of the object, or zero if null
- * @since 2.1
- */
- public static int hashCode(Object obj) {
- // hashCode(Object) retained for performance, as hash code is often critical
- return (obj == null) ? 0 : obj.hashCode();
- }
-
- /**
- * <p>Gets the hash code for multiple objects.</p>
- *
- * <p>This allows a hash code to be rapidly calculated for a number of objects.
- * The hash code for a single object is the <em>not</em> same as {@link #hashCode(Object)}.
- * The hash code for multiple objects is the same as that calculated by an
- * {@code ArrayList} containing the specified objects.</p>
- *
- * <pre>
- * ObjectUtils.hashCodeMulti() = 1
- * ObjectUtils.hashCodeMulti((Object[]) null) = 1
- * ObjectUtils.hashCodeMulti(a) = 31 + a.hashCode()
- * ObjectUtils.hashCodeMulti(a,b) = (31 + a.hashCode()) * 31 + b.hashCode()
- * ObjectUtils.hashCodeMulti(a,b,c) = ((31 + a.hashCode()) * 31 + b.hashCode()) * 31 + c.hashCode()
- * </pre>
- *
- * @param objects the objects to obtain the hash code of, may be {@code null}
- * @return the hash code of the objects, or zero if null
- * @since 3.0
- */
- public static int hashCodeMulti(Object... objects) {
- int hash = 1;
- if (objects != null) {
- for (Object object : objects) {
- hash = hash * 31 + ObjectUtils.hashCode(object);
- }
- }
- return hash;
- }
-
- // Identity ToString
- //-----------------------------------------------------------------------
- /**
- * <p>Gets the toString that would be produced by {@code Object}
- * if a class did not override toString itself. {@code null}
- * will return {@code null}.</p>
- *
- * <pre>
- * ObjectUtils.identityToString(null) = null
- * ObjectUtils.identityToString("") = "java.lang.String@1e23"
- * ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa"
- * </pre>
- *
- * @param object the object to create a toString for, may be
- * {@code null}
- * @return the default toString text, or {@code null} if
- * {@code null} passed in
- */
- public static String identityToString(Object object) {
- if (object == null) {
- return null;
- }
- StringBuffer buffer = new StringBuffer();
- identityToString(buffer, object);
- return buffer.toString();
- }
-
- /**
- * <p>Appends the toString that would be produced by {@code Object}
- * if a class did not override toString itself. {@code null}
- * will throw a NullPointerException for either of the two parameters. </p>
- *
- * <pre>
- * ObjectUtils.identityToString(buf, "") = buf.append("java.lang.String@1e23"
- * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa"
- * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa")
- * </pre>
- *
- * @param buffer the buffer to append to
- * @param object the object to create a toString for
- * @since 2.4
- */
- public static void identityToString(StringBuffer buffer, Object object) {
- if (object == null) {
- throw new NullPointerException("Cannot get the toString of a null identity");
- }
- buffer.append(object.getClass().getName())
- .append('@')
- .append(Integer.toHexString(System.identityHashCode(object)));
- }
-
- // ToString
- //-----------------------------------------------------------------------
- /**
- * <p>Gets the {@code toString} of an {@code Object} returning
- * an empty string ("") if {@code null} input.</p>
- *
- * <pre>
- * ObjectUtils.toString(null) = ""
- * ObjectUtils.toString("") = ""
- * ObjectUtils.toString("bat") = "bat"
- * ObjectUtils.toString(Boolean.TRUE) = "true"
- * </pre>
- *
- * @see StringUtils#defaultString(String)
- * @see String#valueOf(Object)
- * @param obj the Object to {@code toString}, may be null
- * @return the passed in Object's toString, or nullStr if {@code null} input
- * @since 2.0
- */
- public static String toString(Object obj) {
- return obj == null ? "" : obj.toString();
- }
-
- /**
- * <p>Gets the {@code toString} of an {@code Object} returning
- * a specified text if {@code null} input.</p>
- *
- * <pre>
- * ObjectUtils.toString(null, null) = null
- * ObjectUtils.toString(null, "null") = "null"
- * ObjectUtils.toString("", "null") = ""
- * ObjectUtils.toString("bat", "null") = "bat"
- * ObjectUtils.toString(Boolean.TRUE, "null") = "true"
- * </pre>
- *
- * @see StringUtils#defaultString(String,String)
- * @see String#valueOf(Object)
- * @param obj the Object to {@code toString}, may be null
- * @param nullStr the String to return if {@code null} input, may be null
- * @return the passed in Object's toString, or nullStr if {@code null} input
- * @since 2.0
- */
- public static String toString(Object obj, String nullStr) {
- return obj == null ? nullStr : obj.toString();
- }
-
- // Comparable
- //-----------------------------------------------------------------------
- /**
- * <p>Null safe comparison of Comparables.</p>
- *
- * @param <T> type of the values processed by this method
- * @param values the set of comparable values, may be null
- * @return
- * <ul>
- * <li>If any objects are non-null and unequal, the lesser object.
- * <li>If all objects are non-null and equal, the first.
- * <li>If any of the comparables are null, the lesser of the non-null objects.
- * <li>If all the comparables are null, null is returned.
- * </ul>
- */
- public static <T extends Comparable<? super T>> T min(T... values) {
- T result = null;
- if (values != null) {
- for (T value : values) {
- if (compare(value, result, true) < 0) {
- result = value;
- }
- }
- }
- return result;
- }
-
- /**
- * <p>Null safe comparison of Comparables.</p>
- *
- * @param <T> type of the values processed by this method
- * @param values the set of comparable values, may be null
- * @return
- * <ul>
- * <li>If any objects are non-null and unequal, the greater object.
- * <li>If all objects are non-null and equal, the first.
- * <li>If any of the comparables are null, the greater of the non-null objects.
- * <li>If all the comparables are null, null is returned.
- * </ul>
- */
- public static <T extends Comparable<? super T>> T max(T... values) {
- T result = null;
- if (values != null) {
- for (T value : values) {
- if (compare(value, result, false) > 0) {
- result = value;
- }
- }
- }
- return result;
- }
-
- /**
- * <p>Null safe comparison of Comparables.
- * {@code null} is assumed to be less than a non-{@code null} value.</p>
- *
- * @param <T> type of the values processed by this method
- * @param c1 the first comparable, may be null
- * @param c2 the second comparable, may be null
- * @return a negative value if c1 < c2, zero if c1 = c2
- * and a positive value if c1 > c2
- */
- public static <T extends Comparable<? super T>> int compare(T c1, T c2) {
- return compare(c1, c2, false);
- }
-
- /**
- * <p>Null safe comparison of Comparables.</p>
- *
- * @param <T> type of the values processed by this method
- * @param c1 the first comparable, may be null
- * @param c2 the second comparable, may be null
- * @param nullGreater if true {@code null} is considered greater
- * than a non-{@code null} value or if false {@code null} is
- * considered less than a Non-{@code null} value
- * @return a negative value if c1 < c2, zero if c1 = c2
- * and a positive value if c1 > c2
- * @see java.util.Comparator#compare(Object, Object)
- */
- public static <T extends Comparable<? super T>> int compare(T c1, T c2, boolean nullGreater) {
- if (c1 == c2) {
- return 0;
- } else if (c1 == null) {
- return (nullGreater ? 1 : -1);
- } else if (c2 == null) {
- return (nullGreater ? -1 : 1);
- }
- return c1.compareTo(c2);
- }
-
- /**
- * Find the "best guess" middle value among comparables. If there is an even
- * number of total values, the lower of the two middle values will be returned.
- * @param <T> type of values processed by this method
- * @param items to compare
- * @return T at middle position
- * @throws NullPointerException if items is {@code null}
- * @throws IllegalArgumentException if items is empty or contains {@code null} values
- * @since 3.0.1
- */
- public static <T extends Comparable<? super T>> T median(T... items) {
- Validate.notEmpty(items);
- Validate.noNullElements(items);
- TreeSet<T> sort = new TreeSet<T>();
- Collections.addAll(sort, items);
- @SuppressWarnings("unchecked") //we know all items added were T instances
- T result = (T) sort.toArray()[(sort.size() - 1) / 2];
- return result;
- }
-
- /**
- * Find the "best guess" middle value among comparables. If there is an even
- * number of total values, the lower of the two middle values will be returned.
- * @param <T> type of values processed by this method
- * @param comparator to use for comparisons
- * @param items to compare
- * @return T at middle position
- * @throws NullPointerException if items or comparator is {@code null}
- * @throws IllegalArgumentException if items is empty or contains {@code null} values
- * @since 3.0.1
- */
- public static <T> T median(Comparator<T> comparator, T... items) {
- Validate.notEmpty(items, "null/empty items");
- Validate.noNullElements(items);
- Validate.notNull(comparator, "null comparator");
- TreeSet<T> sort = new TreeSet<T>(comparator);
- Collections.addAll(sort, items);
- @SuppressWarnings("unchecked") //we know all items added were T instances
- T result = (T) sort.toArray()[(sort.size() - 1) / 2];
- return result;
- }
-
- // Mode
- //-----------------------------------------------------------------------
- /**
- * Find the most frequently occurring item.
- *
- * @param <T> type of values processed by this method
- * @param items to check
- * @return most populous T, {@code null} if non-unique or no items supplied
- * @since 3.0.1
- */
- public static <T> T mode(T... items) {
- if (ArrayUtils.isNotEmpty(items)) {
- HashMap<T, MutableInt> occurrences = new HashMap<T, MutableInt>(items.length);
- for (T t : items) {
- MutableInt count = occurrences.get(t);
- if (count == null) {
- occurrences.put(t, new MutableInt(1));
- } else {
- count.increment();
- }
- }
- T result = null;
- int max = 0;
- for (Map.Entry<T, MutableInt> e : occurrences.entrySet()) {
- int cmp = e.getValue().intValue();
- if (cmp == max) {
- result = null;
- } else if (cmp > max) {
- max = cmp;
- result = e.getKey();
- }
- }
- return result;
- }
- return null;
- }
-
- // cloning
- //-----------------------------------------------------------------------
- /**
- * <p>Clone an object.</p>
- *
- * @param <T> the type of the object
- * @param obj the object to clone, null returns null
- * @return the clone if the object implements {@link Cloneable} otherwise {@code null}
- * @throws CloneFailedException if the object is cloneable and the clone operation fails
- * @since 3.0
- */
- public static <T> T clone(final T obj) {
- if (obj instanceof Cloneable) {
- final Object result;
- if (obj.getClass().isArray()) {
- final Class<?> componentType = obj.getClass().getComponentType();
- if (!componentType.isPrimitive()) {
- result = ((Object[]) obj).clone();
- } else {
- int length = Array.getLength(obj);
- result = Array.newInstance(componentType, length);
- while (length-- > 0) {
- Array.set(result, length, Array.get(obj, length));
- }
- }
- } else {
- try {
- final Method clone = obj.getClass().getMethod("clone");
- result = clone.invoke(obj);
- } catch (final NoSuchMethodException e) {
- throw new CloneFailedException("Cloneable type "
- + obj.getClass().getName()
- + " has no clone method", e);
- } catch (final IllegalAccessException e) {
- throw new CloneFailedException("Cannot clone Cloneable type "
- + obj.getClass().getName(), e);
- } catch (final InvocationTargetException e) {
- throw new CloneFailedException("Exception cloning Cloneable type "
- + obj.getClass().getName(), e.getCause());
- }
- }
- @SuppressWarnings("unchecked")
- final T checked = (T) result;
- return checked;
- }
-
- return null;
- }
-
- /**
- * <p>Clone an object if possible.</p>
- *
- * <p>This method is similar to {@link #clone(Object)}, but will return the provided
- * instance as the return value instead of {@code null} if the instance
- * is not cloneable. This is more convenient if the caller uses different
- * implementations (e.g. of a service) and some of the implementations do not allow concurrent
- * processing or have state. In such cases the implementation can simply provide a proper
- * clone implementation and the caller's code does not have to change.</p>
- *
- * @param <T> the type of the object
- * @param obj the object to clone, null returns null
- * @return the clone if the object implements {@link Cloneable} otherwise the object itself
- * @throws CloneFailedException if the object is cloneable and the clone operation fails
- * @since 3.0
- */
- public static <T> T cloneIfPossible(final T obj) {
- final T clone = clone(obj);
- return clone == null ? obj : clone;
- }
-
- // Null
- //-----------------------------------------------------------------------
- /**
- * <p>Class used as a null placeholder where {@code null}
- * has another meaning.</p>
- *
- * <p>For example, in a {@code HashMap} the
- * {@link java.util.HashMap#get(java.lang.Object)} method returns
- * {@code null} if the {@code Map} contains {@code null} or if there is
- * no matching key. The {@code Null} placeholder can be used to distinguish
- * between these two cases.</p>
- *
- * <p>Another example is {@code Hashtable}, where {@code null}
- * cannot be stored.</p>
- */
- public static class Null implements Serializable {
- /**
- * Required for serialization support. Declare serialization compatibility with Commons Lang 1.0
- *
- * @see java.io.Serializable
- */
- private static final long serialVersionUID = 7092611880189329093L;
-
- /**
- * Restricted constructor - singleton.
- */
- Null() {
- super();
- }
-
- /**
- * <p>Ensure singleton.</p>
- *
- * @return the singleton value
- */
- private Object readResolve() {
- return ObjectUtils.NULL;
- }
- }
-
-}
+/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.lang3; + +import java.io.Serializable; +import java.lang.reflect.Array; +import java.lang.reflect.InvocationTargetException; +import java.lang.reflect.Method; +import java.util.Collections; +import java.util.Comparator; +import java.util.HashMap; +import java.util.Map; +import java.util.TreeSet; + +import org.apache.commons.lang3.exception.CloneFailedException; +import org.apache.commons.lang3.mutable.MutableInt; + +/** + * <p>Operations on {@code Object}.</p> + * + * <p>This class tries to handle {@code null} input gracefully. + * An exception will generally not be thrown for a {@code null} input. + * Each method documents its behaviour in more detail.</p> + * + * <p>#ThreadSafe#</p> + * @since 1.0 + * @version $Id: ObjectUtils.java 1153350 2011-08-03 05:29:21Z bayard $ + */ +//@Immutable +public class ObjectUtils { + + /** + * <p>Singleton used as a {@code null} placeholder where + * {@code null} has another meaning.</p> + * + * <p>For example, in a {@code HashMap} the + * {@link java.util.HashMap#get(java.lang.Object)} method returns + * {@code null} if the {@code Map} contains {@code null} or if there + * is no matching key. The {@code Null} placeholder can be used to + * distinguish between these two cases.</p> + * + * <p>Another example is {@code Hashtable}, where {@code null} + * cannot be stored.</p> + * + * <p>This instance is Serializable.</p> + */ + public static final Null NULL = new Null(); + + /** + * <p>{@code ObjectUtils} instances should NOT be constructed in + * standard programming. Instead, the static methods on the class should + * be used, such as {@code ObjectUtils.defaultIfNull("a","b");}.</p> + * + * <p>This constructor is public to permit tools that require a JavaBean + * instance to operate.</p> + */ + public ObjectUtils() { + super(); + } + + // Defaulting + //----------------------------------------------------------------------- + /** + * <p>Returns a default value if the object passed is {@code null}.</p> + * + * <pre> + * ObjectUtils.defaultIfNull(null, null) = null + * ObjectUtils.defaultIfNull(null, "") = "" + * ObjectUtils.defaultIfNull(null, "zz") = "zz" + * ObjectUtils.defaultIfNull("abc", *) = "abc" + * ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE + * </pre> + * + * @param <T> the type of the object + * @param object the {@code Object} to test, may be {@code null} + * @param defaultValue the default value to return, may be {@code null} + * @return {@code object} if it is not {@code null}, defaultValue otherwise + */ + public static <T> T defaultIfNull(T object, T defaultValue) { + return object != null ? object : defaultValue; + } + + /** + * <p>Returns the first value in the array which is not {@code null}. + * If all the values are {@code null} or the array is {@code null} + * or empty then {@code null} is returned.</p> + * + * <pre> + * ObjectUtils.firstNonNull(null, null) = null + * ObjectUtils.firstNonNull(null, "") = "" + * ObjectUtils.firstNonNull(null, null, "") = "" + * ObjectUtils.firstNonNull(null, "zz") = "zz" + * ObjectUtils.firstNonNull("abc", *) = "abc" + * ObjectUtils.firstNonNull(null, "xyz", *) = "xyz" + * ObjectUtils.firstNonNull(Boolean.TRUE, *) = Boolean.TRUE + * ObjectUtils.firstNonNull() = null + * </pre> + * + * @param <T> the component type of the array + * @param values the values to test, may be {@code null} or empty + * @return the first value from {@code values} which is not {@code null}, + * or {@code null} if there are no non-null values + * @since 3.0 + */ + public static <T> T firstNonNull(T... values) { + if (values != null) { + for (T val : values) { + if (val != null) { + return val; + } + } + } + return null; + } + + // Null-safe equals/hashCode + //----------------------------------------------------------------------- + /** + * <p>Compares two objects for equality, where either one or both + * objects may be {@code null}.</p> + * + * <pre> + * ObjectUtils.equals(null, null) = true + * ObjectUtils.equals(null, "") = false + * ObjectUtils.equals("", null) = false + * ObjectUtils.equals("", "") = true + * ObjectUtils.equals(Boolean.TRUE, null) = false + * ObjectUtils.equals(Boolean.TRUE, "true") = false + * ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true + * ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false + * </pre> + * + * @param object1 the first object, may be {@code null} + * @param object2 the second object, may be {@code null} + * @return {@code true} if the values of both objects are the same + */ + public static boolean equals(Object object1, Object object2) { + if (object1 == object2) { + return true; + } + if ((object1 == null) || (object2 == null)) { + return false; + } + return object1.equals(object2); + } + + /** + * <p>Compares two objects for inequality, where either one or both + * objects may be {@code null}.</p> + * + * <pre> + * ObjectUtils.notEqual(null, null) = false + * ObjectUtils.notEqual(null, "") = true + * ObjectUtils.notEqual("", null) = true + * ObjectUtils.notEqual("", "") = false + * ObjectUtils.notEqual(Boolean.TRUE, null) = true + * ObjectUtils.notEqual(Boolean.TRUE, "true") = true + * ObjectUtils.notEqual(Boolean.TRUE, Boolean.TRUE) = false + * ObjectUtils.notEqual(Boolean.TRUE, Boolean.FALSE) = true + * </pre> + * + * @param object1 the first object, may be {@code null} + * @param object2 the second object, may be {@code null} + * @return {@code false} if the values of both objects are the same + */ + public static boolean notEqual(Object object1, Object object2) { + return ObjectUtils.equals(object1, object2) == false; + } + + /** + * <p>Gets the hash code of an object returning zero when the + * object is {@code null}.</p> + * + * <pre> + * ObjectUtils.hashCode(null) = 0 + * ObjectUtils.hashCode(obj) = obj.hashCode() + * </pre> + * + * @param obj the object to obtain the hash code of, may be {@code null} + * @return the hash code of the object, or zero if null + * @since 2.1 + */ + public static int hashCode(Object obj) { + // hashCode(Object) retained for performance, as hash code is often critical + return (obj == null) ? 0 : obj.hashCode(); + } + + /** + * <p>Gets the hash code for multiple objects.</p> + * + * <p>This allows a hash code to be rapidly calculated for a number of objects. + * The hash code for a single object is the <em>not</em> same as {@link #hashCode(Object)}. + * The hash code for multiple objects is the same as that calculated by an + * {@code ArrayList} containing the specified objects.</p> + * + * <pre> + * ObjectUtils.hashCodeMulti() = 1 + * ObjectUtils.hashCodeMulti((Object[]) null) = 1 + * ObjectUtils.hashCodeMulti(a) = 31 + a.hashCode() + * ObjectUtils.hashCodeMulti(a,b) = (31 + a.hashCode()) * 31 + b.hashCode() + * ObjectUtils.hashCodeMulti(a,b,c) = ((31 + a.hashCode()) * 31 + b.hashCode()) * 31 + c.hashCode() + * </pre> + * + * @param objects the objects to obtain the hash code of, may be {@code null} + * @return the hash code of the objects, or zero if null + * @since 3.0 + */ + public static int hashCodeMulti(Object... objects) { + int hash = 1; + if (objects != null) { + for (Object object : objects) { + hash = hash * 31 + ObjectUtils.hashCode(object); + } + } + return hash; + } + + // Identity ToString + //----------------------------------------------------------------------- + /** + * <p>Gets the toString that would be produced by {@code Object} + * if a class did not override toString itself. {@code null} + * will return {@code null}.</p> + * + * <pre> + * ObjectUtils.identityToString(null) = null + * ObjectUtils.identityToString("") = "java.lang.String@1e23" + * ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa" + * </pre> + * + * @param object the object to create a toString for, may be + * {@code null} + * @return the default toString text, or {@code null} if + * {@code null} passed in + */ + public static String identityToString(Object object) { + if (object == null) { + return null; + } + StringBuffer buffer = new StringBuffer(); + identityToString(buffer, object); + return buffer.toString(); + } + + /** + * <p>Appends the toString that would be produced by {@code Object} + * if a class did not override toString itself. {@code null} + * will throw a NullPointerException for either of the two parameters. </p> + * + * <pre> + * ObjectUtils.identityToString(buf, "") = buf.append("java.lang.String@1e23" + * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa" + * ObjectUtils.identityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa") + * </pre> + * + * @param buffer the buffer to append to + * @param object the object to create a toString for + * @since 2.4 + */ + public static void identityToString(StringBuffer buffer, Object object) { + if (object == null) { + throw new NullPointerException("Cannot get the toString of a null identity"); + } + buffer.append(object.getClass().getName()) + .append('@') + .append(Integer.toHexString(System.identityHashCode(object))); + } + + // ToString + //----------------------------------------------------------------------- + /** + * <p>Gets the {@code toString} of an {@code Object} returning + * an empty string ("") if {@code null} input.</p> + * + * <pre> + * ObjectUtils.toString(null) = "" + * ObjectUtils.toString("") = "" + * ObjectUtils.toString("bat") = "bat" + * ObjectUtils.toString(Boolean.TRUE) = "true" + * </pre> + * + * @see StringUtils#defaultString(String) + * @see String#valueOf(Object) + * @param obj the Object to {@code toString}, may be null + * @return the passed in Object's toString, or nullStr if {@code null} input + * @since 2.0 + */ + public static String toString(Object obj) { + return obj == null ? "" : obj.toString(); + } + + /** + * <p>Gets the {@code toString} of an {@code Object} returning + * a specified text if {@code null} input.</p> + * + * <pre> + * ObjectUtils.toString(null, null) = null + * ObjectUtils.toString(null, "null") = "null" + * ObjectUtils.toString("", "null") = "" + * ObjectUtils.toString("bat", "null") = "bat" + * ObjectUtils.toString(Boolean.TRUE, "null") = "true" + * </pre> + * + * @see StringUtils#defaultString(String,String) + * @see String#valueOf(Object) + * @param obj the Object to {@code toString}, may be null + * @param nullStr the String to return if {@code null} input, may be null + * @return the passed in Object's toString, or nullStr if {@code null} input + * @since 2.0 + */ + public static String toString(Object obj, String nullStr) { + return obj == null ? nullStr : obj.toString(); + } + + // Comparable + //----------------------------------------------------------------------- + /** + * <p>Null safe comparison of Comparables.</p> + * + * @param <T> type of the values processed by this method + * @param values the set of comparable values, may be null + * @return + * <ul> + * <li>If any objects are non-null and unequal, the lesser object. + * <li>If all objects are non-null and equal, the first. + * <li>If any of the comparables are null, the lesser of the non-null objects. + * <li>If all the comparables are null, null is returned. + * </ul> + */ + public static <T extends Comparable<? super T>> T min(T... values) { + T result = null; + if (values != null) { + for (T value : values) { + if (compare(value, result, true) < 0) { + result = value; + } + } + } + return result; + } + + /** + * <p>Null safe comparison of Comparables.</p> + * + * @param <T> type of the values processed by this method + * @param values the set of comparable values, may be null + * @return + * <ul> + * <li>If any objects are non-null and unequal, the greater object. + * <li>If all objects are non-null and equal, the first. + * <li>If any of the comparables are null, the greater of the non-null objects. + * <li>If all the comparables are null, null is returned. + * </ul> + */ + public static <T extends Comparable<? super T>> T max(T... values) { + T result = null; + if (values != null) { + for (T value : values) { + if (compare(value, result, false) > 0) { + result = value; + } + } + } + return result; + } + + /** + * <p>Null safe comparison of Comparables. + * {@code null} is assumed to be less than a non-{@code null} value.</p> + * + * @param <T> type of the values processed by this method + * @param c1 the first comparable, may be null + * @param c2 the second comparable, may be null + * @return a negative value if c1 < c2, zero if c1 = c2 + * and a positive value if c1 > c2 + */ + public static <T extends Comparable<? super T>> int compare(T c1, T c2) { + return compare(c1, c2, false); + } + + /** + * <p>Null safe comparison of Comparables.</p> + * + * @param <T> type of the values processed by this method + * @param c1 the first comparable, may be null + * @param c2 the second comparable, may be null + * @param nullGreater if true {@code null} is considered greater + * than a non-{@code null} value or if false {@code null} is + * considered less than a Non-{@code null} value + * @return a negative value if c1 < c2, zero if c1 = c2 + * and a positive value if c1 > c2 + * @see java.util.Comparator#compare(Object, Object) + */ + public static <T extends Comparable<? super T>> int compare(T c1, T c2, boolean nullGreater) { + if (c1 == c2) { + return 0; + } else if (c1 == null) { + return (nullGreater ? 1 : -1); + } else if (c2 == null) { + return (nullGreater ? -1 : 1); + } + return c1.compareTo(c2); + } + + /** + * Find the "best guess" middle value among comparables. If there is an even + * number of total values, the lower of the two middle values will be returned. + * @param <T> type of values processed by this method + * @param items to compare + * @return T at middle position + * @throws NullPointerException if items is {@code null} + * @throws IllegalArgumentException if items is empty or contains {@code null} values + * @since 3.0.1 + */ + public static <T extends Comparable<? super T>> T median(T... items) { + Validate.notEmpty(items); + Validate.noNullElements(items); + TreeSet<T> sort = new TreeSet<T>(); + Collections.addAll(sort, items); + @SuppressWarnings("unchecked") //we know all items added were T instances + T result = (T) sort.toArray()[(sort.size() - 1) / 2]; + return result; + } + + /** + * Find the "best guess" middle value among comparables. If there is an even + * number of total values, the lower of the two middle values will be returned. + * @param <T> type of values processed by this method + * @param comparator to use for comparisons + * @param items to compare + * @return T at middle position + * @throws NullPointerException if items or comparator is {@code null} + * @throws IllegalArgumentException if items is empty or contains {@code null} values + * @since 3.0.1 + */ + public static <T> T median(Comparator<T> comparator, T... items) { + Validate.notEmpty(items, "null/empty items"); + Validate.noNullElements(items); + Validate.notNull(comparator, "null comparator"); + TreeSet<T> sort = new TreeSet<T>(comparator); + Collections.addAll(sort, items); + @SuppressWarnings("unchecked") //we know all items added were T instances + T result = (T) sort.toArray()[(sort.size() - 1) / 2]; + return result; + } + + // Mode + //----------------------------------------------------------------------- + /** + * Find the most frequently occurring item. + * + * @param <T> type of values processed by this method + * @param items to check + * @return most populous T, {@code null} if non-unique or no items supplied + * @since 3.0.1 + */ + public static <T> T mode(T... items) { + if (ArrayUtils.isNotEmpty(items)) { + HashMap<T, MutableInt> occurrences = new HashMap<T, MutableInt>(items.length); + for (T t : items) { + MutableInt count = occurrences.get(t); + if (count == null) { + occurrences.put(t, new MutableInt(1)); + } else { + count.increment(); + } + } + T result = null; + int max = 0; + for (Map.Entry<T, MutableInt> e : occurrences.entrySet()) { + int cmp = e.getValue().intValue(); + if (cmp == max) { + result = null; + } else if (cmp > max) { + max = cmp; + result = e.getKey(); + } + } + return result; + } + return null; + } + + // cloning + //----------------------------------------------------------------------- + /** + * <p>Clone an object.</p> + * + * @param <T> the type of the object + * @param obj the object to clone, null returns null + * @return the clone if the object implements {@link Cloneable} otherwise {@code null} + * @throws CloneFailedException if the object is cloneable and the clone operation fails + * @since 3.0 + */ + public static <T> T clone(final T obj) { + if (obj instanceof Cloneable) { + final Object result; + if (obj.getClass().isArray()) { + final Class<?> componentType = obj.getClass().getComponentType(); + if (!componentType.isPrimitive()) { + result = ((Object[]) obj).clone(); + } else { + int length = Array.getLength(obj); + result = Array.newInstance(componentType, length); + while (length-- > 0) { + Array.set(result, length, Array.get(obj, length)); + } + } + } else { + try { + final Method clone = obj.getClass().getMethod("clone"); + result = clone.invoke(obj); + } catch (final NoSuchMethodException e) { + throw new CloneFailedException("Cloneable type " + + obj.getClass().getName() + + " has no clone method", e); + } catch (final IllegalAccessException e) { + throw new CloneFailedException("Cannot clone Cloneable type " + + obj.getClass().getName(), e); + } catch (final InvocationTargetException e) { + throw new CloneFailedException("Exception cloning Cloneable type " + + obj.getClass().getName(), e.getCause()); + } + } + @SuppressWarnings("unchecked") + final T checked = (T) result; + return checked; + } + + return null; + } + + /** + * <p>Clone an object if possible.</p> + * + * <p>This method is similar to {@link #clone(Object)}, but will return the provided + * instance as the return value instead of {@code null} if the instance + * is not cloneable. This is more convenient if the caller uses different + * implementations (e.g. of a service) and some of the implementations do not allow concurrent + * processing or have state. In such cases the implementation can simply provide a proper + * clone implementation and the caller's code does not have to change.</p> + * + * @param <T> the type of the object + * @param obj the object to clone, null returns null + * @return the clone if the object implements {@link Cloneable} otherwise the object itself + * @throws CloneFailedException if the object is cloneable and the clone operation fails + * @since 3.0 + */ + public static <T> T cloneIfPossible(final T obj) { + final T clone = clone(obj); + return clone == null ? obj : clone; + } + + // Null + //----------------------------------------------------------------------- + /** + * <p>Class used as a null placeholder where {@code null} + * has another meaning.</p> + * + * <p>For example, in a {@code HashMap} the + * {@link java.util.HashMap#get(java.lang.Object)} method returns + * {@code null} if the {@code Map} contains {@code null} or if there is + * no matching key. The {@code Null} placeholder can be used to distinguish + * between these two cases.</p> + * + * <p>Another example is {@code Hashtable}, where {@code null} + * cannot be stored.</p> + */ + public static class Null implements Serializable { + /** + * Required for serialization support. Declare serialization compatibility with Commons Lang 1.0 + * + * @see java.io.Serializable + */ + private static final long serialVersionUID = 7092611880189329093L; + + /** + * Restricted constructor - singleton. + */ + Null() { + super(); + } + + /** + * <p>Ensure singleton.</p> + * + * @return the singleton value + */ + private Object readResolve() { + return ObjectUtils.NULL; + } + } + +} |