代码 

package day3;

public class Demo2 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		//		for (int i = 0; i < 10; i++) {
		//			for (int j = 0; j < 10; j++) {
		//				System.out.print("外："+i+"内："+j);
		//			}
		//			System.out.println();
		//		}
		
		int n = 6; 
		int [][] arr = new int [n+1][n+1];
		for (int i = 1; i < arr.length; i++) {
			for (int j = 1; j <=i; j++) {
				if(i==1||i==j) {
					arr[i][j]=1;
				}else {
					arr[i][j]=arr[i-1][j]+arr[i-1][j-1];
				}
			}
		}
		for (int i = 1; i < arr.length; i++) {
			for (int j = 1; j <=i; j++) {
				System.out.print(arr[i][j]+",");
			}
			System.out.println();
		}	
	}
}

i内层，j外层

核心：每个位置的值为(i-1,j)位置的值加(i-1,j-1)位置的值

运行结果