使用兩層巢狀迴圈，實現行列迴圈列印輸出，形成簡單圖案。

程式碼如下：

//JHTP Exercise 4.29:Square of Asterisks
//by [email protected]
/**(Square of Asterisks) Write an application that prompts the user to enter the size of the side
of a square, then displays a hollow square of that size made of asterisks. Your program should work
for squares of all side lengths between 1 and 20.*/
import java.util.Scanner;

public class SquareOfAsterisks {

	public static void main (String[] args){
	Scanner input=new Scanner(System.in);
	System.out.print("請輸入要輸出的正方形大小（整數）：");
	int size=input.nextInt();
	int number=1;
	int sentinel=1;
	while (sentinel<=size){
		while (number<=size){
			System.out.print("*");
			number++;
			}
		System.out.print("\n");
		number=1;
		sentinel++;
	}
	
		}
}
 

執行截圖：

請輸入要輸出的正方形大小（整數）：10
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