7、数组

1、一维数组

• 声明

        //声明1
        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]);
        }

• 数组如果仅仅是声明，没有赋值，但是会有个默认值

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

• 数组越界异常

        // [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]);

  2、二维数组

        int[][] score = new int[][]{
                {1,2,3},
                {4,5,6,8},
                {7,8,9}};
        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();
        }