问修复在Java中接受用户输入时的无限循环

EN

import java.io.*; 

class Choice
{ 
public static void main (String[] args) 
{  
    String input = ""; 
    Boolean keep_going = true;
    while (keep_going)
    {
        input = "";
        System.out.println("Welcome to my program! Would you like to:");
        System.out.println("1. Say hi.");
        System.out.println("2. Find out my favourite colour.");
        System.out.println("3. End the program.");
        System.out.println(">");
        System.out.print( "> " );
        InputStreamReader isr = new InputStreamReader( System.in );
        BufferedReader buffer = new BufferedReader( isr );
        try
        { 
            input = buffer.readLine();
            buffer.close() ; 
        } 
        catch (IOException e ) 
        { 
            System.out.println(e);  
        } 
        switch (input)
        {
            case "1": System.out.println("Hi!"); break;
            case "2": System.out.println("My favourite colour is blue!"); break;
            case "3": return;
            default : System.out.println(input + " is not a valid option. Please try again.");
        }
    }


}