Add the most useful Apache Commons utils

compiler/java/com/google/dart/compiler/util/apache/ObjectUtils.java

Index: compiler/java/com/google/dart/compiler/util/apache/ObjectUtils.java
diff --git a/compiler/java/com/google/dart/compiler/util/apache/ObjectUtils.java b/compiler/java/com/google/dart/compiler/util/apache/ObjectUtils.java
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+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/*
+ * 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 com.google.dart.compiler.util.apache;
+
+import com.google.dart.compiler.util.apache.exception.CloneFailedException;
+import com.google.dart.compiler.util.apache.mutable.MutableInt;
+
+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;
+
+/**
+ * <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>
+ * NOTICE: This file is modified copy of its original Apache library.
+ * It was moved to the different package, and changed to reduce number of dependencies.
+ *
+ * <p>#ThreadSafe#</p>
+ * @since 1.0
+ * @version $Id: ObjectUtils.java 1199894 2011-11-09 17:53:59Z ggregory $
+ */
+//@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;
+        }
+    }
+
+}