001    /*
002     * Created on May 13, 2007
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
005     * the License. You may obtain a copy of the License at
006     *
007     * http://www.apache.org/licenses/LICENSE-2.0
008     *
009     * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
010     * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
011     * specific language governing permissions and limitations under the License.
012     *
013     * Copyright @2007-2011 the original author or authors.
014     */
015    package org.fest.util;
016    
017    import static java.lang.System.arraycopy;
018    
019    import java.lang.reflect.Array;
020    import java.util.*;
021    
022    /**
023     * Utility methods related to arrays.
024     *
025     * @author Alex Ruiz
026     * @author Joel Costigliola
027     */
028    public class Arrays {
029    
030      private static final ArrayFormatter formatter = new ArrayFormatter();
031    
032      /**
033       * Returns {@code true} if the given object is not {@code null} and is an array.
034       * @param o the given object.
035       * @return {@code true} if the given object is not {@code null} and is an array, otherwise {@code false}.
036       */
037      public static boolean isArray(Object o) {
038        return o != null && o.getClass().isArray();
039      }
040    
041      /**
042       * Returns {@code true} if the given array is {@code null} or empty.
043       * @param <T> the type of elements of the array.
044       * @param array the array to check.
045       * @return {@code true} if the given array is {@code null} or empty, otherwise {@code false}.
046       */
047      public static <T> boolean isEmpty(T[] array) {
048        return array == null || !hasElements(array);
049      }
050    
051      /**
052       * Returns an array containing the given arguments.
053       * @param <T> the type of the array to return.
054       * @param values the values to store in the array.
055       * @return an array containing the given arguments.
056       */
057      public static <T> T[] array(T... values) {
058        return values;
059      }
060    
061      /**
062       * Returns the {@code String} representation of the given array, or {@code null} if the given object is either
063       * {@code null} or not an array. This method supports arrays having other arrays as elements.
064       * @param array the object that is expected to be an array.
065       * @return the {@code String} representation of the given array.
066       */
067      public static String format(Object array) {
068        return formatter.format(array);
069      }
070    
071      /**
072       * Returns a new array containing the non-null elements of the given array. This method returns an empty array if the
073       * given array has only {@code null} elements or if it is empty. This method returns {@code null} if the given array
074       * is {@code null}.
075       * @param <T> the type of elements of the array.
076       * @param array the array we want to extract the non-null elements from.
077       * @return a new array containing the non-null elements of the given array, or {@code null} if the given array is
078       * {@code null}.
079       * @since 1.1.3
080       */
081      @SuppressWarnings("unchecked")
082      public static <T> T[] nonNullElements(T[] array) {
083        if (array == null) return null;
084        List<T> nonNullElements = new ArrayList<T>();
085        for (T o : array)
086          if (o != null) nonNullElements.add(o);
087        int elementCount = nonNullElements.size();
088        T[] newArray = (T[]) Array.newInstance(array.getClass().getComponentType(), elementCount);
089        arraycopy(nonNullElements.toArray(), 0, newArray, 0, elementCount);
090        return newArray;
091      }
092    
093      /**
094       * Returns {@code true} if the given array has only {@code null} elements, {@code false} otherwise. If given array is
095       * empty, this method returns {@code true}.
096       * @param <T> the type of elements of the array.
097       * @param array the given array. <b>It must not be null</b>.
098       * @return {@code true} if the given array has only {@code null} elements or is empty, {@code false} otherwise.
099       * @throws NullPointerException if the given array is {@code null}.
100       * @since 1.1.3
101       */
102      public static <T> boolean hasOnlyNullElements(T[] array) {
103        if (array == null) throw new NullPointerException("The array to check should not be null");
104        if (!hasElements(array)) return false;
105        for (T o : array)
106          if (o != null) return false;
107        return true;
108      }
109    
110      private static <T> boolean hasElements(T[] array) {
111        return array.length > 0;
112      }
113    
114      /**
115       * Copies the specified array, truncating or padding with nulls (if necessary) so the copy has the specified length.
116       * For all indices that are valid in both the original array and the copy, the two arrays will contain identical
117       * values. For any indices that are valid in the copy but not the original, the copy will contain {@code null}. Such
118       * indices will exist if and only if the specified length is greater than that of the original array.
119       * @param <T> the component type of the array.
120       * @param original the array to be copied.
121       * @param newLength the length of the copy to be returned.
122       * @return a copy of the original array, truncated or padded with nulls to obtain the specified length.
123       * @throws NegativeArraySizeException if {@code newLength} is negative.
124       * @throws NullPointerException if {@code original} is {@code null}.
125       * @since 1.1.5
126       */
127      @SuppressWarnings("unchecked")
128      public static <T> T[] copyOf(T[] original, int newLength) {
129        // TODO test
130        T[] copy = (T[]) Array.newInstance(original.getClass().getComponentType(), newLength);
131        arraycopy(original, 0, copy, 0, Math.min(original.length, newLength));
132        return copy;
133      }
134    
135      private Arrays() {}
136    }