Create a type-safe generic array. - Android java.lang

Android examples for java.lang:array type

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Description

Create a type-safe generic array.

Demo Code

/*/*  ww  w . j a  v  a 2s .  c  om*/
 * 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.java2s;

public class Main {
    /**
     * <p>Create a type-safe generic array.</p>
     *
     * <p>The Java language does not allow an array to be created from a generic type:</p>
     *
     * <pre>
    public static &lt;T&gt; T[] createAnArray(int size) {
        return new T[size]; // compiler error here
    }
    public static &lt;T&gt; T[] createAnArray(int size) {
        return (T[])new Object[size]; // ClassCastException at runtime
    }
     * </pre>
     *
     * <p>Therefore new arrays of generic types can be created with this method.
     * For example, an array of Strings can be created:</p>
     *
     * <pre>
    String[] array = ArrayUtils.toArray("1", "2");
    String[] emptyArray = ArrayUtils.&lt;String&gt;toArray();
     * </pre>
     *
     * <p>The method is typically used in scenarios, where the caller itself uses generic types
     * that have to be combined into an array.</p>
     *
     * <p>Note, this method makes only sense to provide arguments of the same type so that the
     * compiler can deduce the type of the array itself. While it is possible to select the
     * type explicitly like in
     * <code>Number[] array = ArrayUtils.&lt;Number&gt;toArray(Integer.valueOf(42), Double.valueOf(Math.PI))</code>,
     * there is no real advantage when compared to
     * <code>new Number[] {Integer.valueOf(42), Double.valueOf(Math.PI)}</code>.</p>
     *
     * @param  <T>   the array's element type
     * @param  items  the varargs array items, null allowed
     * @return the array, not null unless a null array is passed in
     * @since  3.0
     */
    public static <T> T[] toArray(final T... items) {
        return items;
    }
}

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