字串反轉 

import java.util.*;  
public class Main{  
    public static void main(String[] args){  
        Scanner in =new Scanner(System.in);  
        while(in.hasNext()){  
            String line=in.nextLine();//next()是遇到空格；nextLine()是遇到回車  
            StringBuffer sb=new StringBuffer(line);  
            sb.reverse();  
            System.out.println(sb.toString());  
        }  
    }  
}  
 

倒三角輸出

public class Test {
	public static void main(String[] args) {
		int i = 0;
		for (i = 7; i >= 1; i -= 2) {
			for (int k = (7 - i) / 2; k >= 1; k--){
				System.out.print(" ");
			}
			for (int j = i; j >= 1; j--){
				System.out.print("*");
			}
			System.out.println();
		}
	}
}