一、二维数组的定义

public class TwoArrayTest {public static void main(String[] args) {//二维数组声明与初始化//方式1：静态初始化int[][] arr = new int[][]{{1,2,3},{1,2,3},{1,2,3}};//方式2：动态初始化int[][] arr2 = new int[3][3];arr2[0][1] = 4;//数组元素调用System.out.println(arr2[0][1]);//数组的长度System.out.println(arr2.length);System.out.println(arr2[0].length);//数组的遍历for (int i = 0; i < arr.length; i++) {for (int j = 0; j < arr[i].length; j++) {System.out.print(arr[i][j]);}System.out.println();}//数组元素的默认初始化值/*** 外层元素：默认存储的是地址值* 内层元素：默认存储的与一维数组默认值相同*/int[][] arr3 = new int[2][1];System.out.println(arr3[0]);//地址值System.out.println(arr3[0][0]);//0}
}

 二、二维数组练习

2.1、求元素总和 

public class ArrayExer04 {public static void main(String[] args) {int[][] arr = {{3,5,8},{12,9},{7,0,6,4}};//记录元素总和int sum = 0;for (int i = 0; i < arr.length; i++) {for (int j = 0; j < arr[i].length; j++) {System.out.print(arr[i][j] + "\t");sum += arr[i][j];}System.out.println();}System.out.println("元素总和为:" + sum);}
}