Java语言程序设计（基础篇）第十版 5.17

public class J5_17 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		java.util.Scanner input = new java.util.Scanner(System.in);
		System.out.print("Enter the number of lines: ");
		int line = input.nextInt();
		
		if(line <1 && line >15) {
			System.out.println("You must enter a number from 1 ~ 15");
			System.exit(0);
		}
		
		for(int r =1;r<=line;r++) {
		
			for(int c=1;c<=line-r;c++)
				System.out.print("   ");
			
			for(int num =r;num>=1;num--)
				 System.out.print((num >= 10) ? " " + num : "  " + num);

            for (int num = 2; num <= r; num++)
               System.out.print((num >= 10) ? " " + num : "  " + num);
            System.out.println();

		}
	
		
	}
}