for循环的分析

public class Try {
    public static void main(String[]args){
        int [][] a = {{1,2,3},{4,5,6},{7,8,9}};
        int i,j,s = 0;
        for ( i=0;i<3;i++){
            System.out.println("===i的值=== "+i);
            for ( j=0;j<i+1;j++){
                System.out.println("---j的值--- "+j);
                s = s+a[2-i][2-j];
                System.out.println("此时的i为 "+i);
                System.out.println("此时的j为 "+j);
                System.out.println("输出a[2-i][2-j] = "+a[2-i][2-j]);
                System.out.println("*****输出 "+s);
            }
        }
        System.out.println("输出s的值 "+s);
    }
}