==多维数组练习：==
image
package day07;
public class ArrayTest {
public static void main(String[] args) {
int[][] arr = new int[][] {{3,5,8},{12,9},{7,0,6,4}};
int sum = 0;
for(int i = 0;i < arr.length;i++) {
for(int j = 0;j < arr[i].length;j++) {
sum += arr[i][j];
}
}
System.out.println("sum=" + sum);
}
}
2.
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int[] x,y[];
==
int[] x;
int[] y[];
自动类型转换、强制类型提升
3.
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package day07;
public class YangHuiTest1 {
public static void main(String[] args) {
//1.声明并初始化数组
int[][] yangHui = new int[10][];
//2.给数组的元素赋值
for(int i = 0;i < yangHui.length;i++) {
yangHui[i] = new int[i + 1];
//2.1给首末元素赋值
yangHui[i][0] = yangHui[i][i] = 1;
//2.2给非首末元素赋值
if(i > 1) {
for(int j = 1;j < yangHui[i].length - 1; j++) {
yangHui[i][j] = yangHui[i - 1][j - 1] + yangHui[i - 1][j];
}
}
}
//3.遍历二维数组
for(int i = 0;i < yangHui.length;i++) {
for(int j = 0;j <yangHui[i].length;j++) {
System.out.print(yangHui[i][j]);
}
System.out.println();
}
}
}
