2-5、数组

语雀原文链接

1、一维数组

• 数组如果仅仅是声明，没有赋值，但是会有个默认值
• int[] 默认是0
• String[] 默认是null

        //声明1,默认[0,0,0]
        int[] a = new int[3];
        for(int i = 0 ; i < a.length ; i++){
            System.out.println(a[i]);
        }

      	// 声明2,默认[0,0,0]
        int a[] = new int[3];
        System.out.println(Arrays.toString(a));
        
        // [null,null]
        String[] b = new String[2];
        for(int i = 0 ; i < b.length ; i++){
            System.out.println(b[i]);
        }

• 声明+赋值

        //声明1 先声明 后赋值
        int[] a = new int[3];
        a[0] = 3;
        a[1] = 4;
        a[2] = 5;

        //声明2
        int[] b = new int[]{3, 4, 5};

        //声明3
        int[] c = {3, 4, 5};

        //遍历输出
        for (int i = 0; i < c.length; i++) {
            System.out.println(c[i]);
        }

• 数组越界异常ArrayIndexOutOfBoundsException

        // [null,null]
        String[] a = new String[2];
        // null
        System.out.println(a[0]);
        // null
        System.out.println(a[1]);
        // java.lang.ArrayIndexOutOfBoundsException
        System.out.println(a[2]);


        System.out.println("aaaaaaa");

2、二维数组

        int[][] score = new int[][]{
                {1, 2, 3},
                {4, 5, 6, 8},
                {7, 8, 9}
        };
        System.out.println(score[0][1]);
        System.out.println(score[1][1]);
        System.out.println(score.length);
        System.out.println(score[1].length);
        System.out.println(score[0].length);


        for (int i = 0; i < score.length; i++) {
            for (int j = 0; j < score[i].length; j++) {
                System.out.print(score[i][j] + " ");
            }
            System.out.println();
        }