要点Java19 java.util.Arrays

来源：互联网发布：软件开发与编程的区别编辑：程序博客网时间：2024/05/21 15:45

Arrays 数组帮助类

示例程序(JUnit演示)

数组转化为List

    @Test    public void testUserArraysChangeArraytoList() {        // 类Arrays        // public static <T> List<T> asList(T... a)         // Returns a fixed-size list backed by the specified array        List<Integer> testList = Arrays.asList(1, 2, 3);        assertEquals("生成大小为3的List", 3, testList.size());        List<Integer> testList1 = Arrays.asList(1, 2);        assertEquals("生成大小为2的List", 2, testList1.size());    }    @Test(expected = UnsupportedOperationException.class)    public void isFixedList() {        // 类Arrays        // public static <T> List<T> asList(T... a)         // Returns a fixed-size list backed by the specified array        Integer[] test = {1,2,3};        List<Integer> testList = Arrays.asList(test);        assertEquals("生成大小为3的List", 3, testList.size());        testList.add(4);//throw UnsupportedOperationException    }

排序

    @Test    public void testSort() {        // 类Arrays        // void java.util.Arrays.sort(Object[] a)        // 排序        Integer[] test = {3,2,1};        Arrays.sort(test);        assertEquals( 1, test[0].intValue() );    }

其他方法

    @Test    public void testEquals() {          Integer[] test1 = {3,2,1};        Integer[] test2 = {3,2,1};          Integer[] test3 = {1,2,3};          //equals        assertTrue(Arrays.equals(test1, test2));        assertFalse(Arrays.equals(test1, test3));        //toString        assertEquals( "[3, 2, 1]", Arrays.toString(test1) );        //copyOf        assertEquals( "[3, 2]", Arrays.toString(Arrays.copyOf(test1, 2)) );        //fill        Arrays.fill(test1, 2);        assertEquals( "[2, 2, 2]", Arrays.toString(test1) );    }

环境 jdk1.6 window7 junit4

0 0