java数组

数组

1、一维数组

        int[] ns = { 1, 4, 9, 16, 25 };
        for (int i=0;i<ns.length;i++){
            sum = sum + ns[i];
        }
        System.out.printf("数组加和为%d",sum);
        // 遍历数组获取数组的每个值
        for (int one : ns){
            System.out.println(one);
        }
        // 倒序输出数组的每个元素
        for (int i=ns.length-1;i>-1;i--){
            System.out.println(ns[i]);
        }
        // 使用for each 实现数组元素加和
        for (int one :ns){
            sum = sum + one;
        }
        System.out.printf("数组元素和为%d",sum);

2、二维数组

// 二维数组
        int[][] ns2 = {{1,2,3},{4,5,6},{7,8,9}
        };
        System.out.println(ns2.length);
        int[] arr0 = ns2[0];
        System.out.println(Arrays.toString(arr0));
        System.out.println(ns2[0][0]);
        for (int[] arr:ns2){
            for (int one:arr){
                System.out.print(one);
                System.out.print(", ");
            }
            System.out.println();
        }
        // java内置标准库打印二维数据Arrays.deepToString()
        System.out.println(Arrays.deepToString(ns2));

3、三维数组

// 三维数组
        int[][][] ns3 = {
                {
                        {1,2,3},
                        {4,5,6}
                },
                {
                        {'a','b','c'},
                        {'d','e','f'}
                }
        };
        System.out.println(ns3[0][1][0]);

小练习：

　　

 // 二维数据练习
        // 用二维数组表示的学生成绩:
        int[][] scores = {
                { 82, 90, 91 },
                { 68, 72, 64 },
                { 95, 91, 89 },
                { 67, 52, 60 },
                { 79, 81, 85 },
        };
        double sumAverage = 0;
        for (int[] arr:scores){
            int sum = 0;
            for (int store:arr){
                sum = sum + store;
            }
            sumAverage = sumAverage + sum / 3.0;
        }
        double average = 0;
        average = sumAverage / scores.length;
        System.out.println(average);
        if (Math.abs(average - 77.733333) < 0.000001) {
            System.out.println("测试成功");
        } else {
            System.out.println("测试失败");
        }

参考：https://www.liaoxuefeng.com/wiki/1252599548343744/1259544232593792#0