com.feilong.core.lang.ArrayUtil.java Source code

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/*
 * Copyright (C) 2008 feilong
 *
 * Licensed 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.feilong.core.lang;

import java.lang.reflect.Array;

import org.apache.commons.lang3.Validate;

/**
 * .
 * 
 * <p>
 * detect array,object is an instanceof boolean[], byte[], short[], char[], int[], long[], float[], double[], or
 * Object[],
 * 
 * <br>
 * :Object[]  Integer/String...User. instanceof Object[],?primitive ,instanceof Object[];<br>
 * so depending on how you want to handle nested arrays, it can get complicated.
 * </p>
 * 
 * <h3>??:</h3>
 * <blockquote>
 * <ol>
 * <li>{@link #getElement(Object, int)},?</li>
 * </ol>
 * </blockquote>
 * 
 * 
 * <h3>??:</h3>
 * 
 * <blockquote>
 * <ul>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(boolean[], boolean)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(byte[], byte)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(char[], char)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(double[], double)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(float[], float)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(int[], int)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(long[], long)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(Object[], Object)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(short[], short)}</li>
 * <li>{@link org.apache.commons.lang3.ArrayUtils#contains(double[], double, double)}</li>
 * </ul>
 * </blockquote>
 *
 * @author <a href="http://feitianbenyue.iteye.com/">feilong</a>
 * @see org.apache.commons.lang3.ArrayUtils
 * @since 1.4.0
 */
public final class ArrayUtil {

    /** Don't let anyone instantiate this class. */
    private ArrayUtil() {
        //AssertionError?. ?????. ???.
        //see Effective Java 2nd
        throw new AssertionError("No " + getClass().getName() + " instances for you!");
    }

    /**
     *  <code>array</code>  <code>index</code> .
     * 
     * <p>
     * (Returns the value of the indexed component in the specified array object. <br>
     * The value is automatically wrapped in an object if it has a primitive type.)
     * </p>
     * 
     * <pre class="code">
     * 
     * Example 1:
     * 
     * Object array = new String[] { "jinxin", "feilong", "1" };
     * LOGGER.info("" + ArrayUtil.getElement(array, 2));
     * 
     * :1
     * </pre>
     *
     * @param <T>
     *            the generic type
     * @param array
     *            
     * @param index
     *            
     * @return ?{@code index}, <code>array</code> , {@link ArrayIndexOutOfBoundsException}
     * @see java.lang.reflect.Array#get(Object, int)
     */
    @SuppressWarnings("unchecked")
    public static <T> T getElement(Object array, int index) {
        return (T) Array.get(array, index);
    }

    /**
     *  <code>componentType</code> ?  <code>length</code>.
     * 
     * <h3>:</h3>
     * 
     * <blockquote>
     * 
     * <pre class="code">
     * assertArrayEquals(new Integer[] {}, ArrayUtil.newArray(Integer.class, 0));
     * assertArrayEquals(new Integer[] { null, null, null }, ArrayUtil.newArray(Integer.class, 3));
     * </pre>
     * 
     * </blockquote>
     *
     * @param <T>
     *            the generic type
     * @param componentType
     *            the component type
     * @param length
     *            the length of the new array
     * @return  <code>componentType</code> null, {@link NullPointerException}<br>
     *          {@code length < 0} , {@link IllegalArgumentException}<br>
     * @see java.lang.reflect.Array#newInstance(Class, int)
     * @see java.lang.reflect.Array#newInstance(Class, int...)
     * @see "com.google.common.collect#newArray(Class, int)"
     * @since 1.6.1
     */
    @SuppressWarnings("unchecked")
    public static <T> T[] newArray(Class<T> componentType, int length) {
        Validate.notNull(componentType, "componentType can't be null!");
        Validate.isTrue(length >= 0, "length:[%s],must >=0", length);
        return (T[]) Array.newInstance(componentType, length);
    }

}