[20160730]while 条件的死循环和正常循环对比

正常循环

import java.io.*;
import java.util.*;

public class MyPrintStreamTest3{
  public static void main(String[] args) {
    BufferedReader br = new BufferedReader(  new InputStreamReader(System.in) );
    String s = null;

  try
  {
    PrintWriter log = new PrintWriter( new FileWriter("D://javalearning//MYIO//log4j.txt",true) );
    while((s = br.readLine())!=null){
      if (s.equalsIgnoreCase("exit")) break;
       System.out.println(s.toUpperCase());
       log.println("--------");
       log.println(s.toUpperCase());
       log.flush();
    }
    log.println("=="+new Date()+"==");
    log.flush();
    log.close();

  }
  catch (IOException e)
  {
     e.printStackTrace();
  }
}
}

死循环

import java.io.*;
import java.util.*;

public class MyPrintStreamTest3{
  public static void main(String[] args) {
    BufferedReader br = new BufferedReader(  new InputStreamReader(System.in) );
    String s = null;

  try
  {
    PrintWriter log = new PrintWriter( new FileWriter("D://javalearning//MYIO//log4j.txt",true) );
    s = br.readLine();
    while(s!=null){
      if (s.equalsIgnoreCase("exit")) break;
       System.out.println(s.toUpperCase());
       log.println("--------");
       log.println(s.toUpperCase());
       log.flush();
    }
    log.println("=="+new Date()+"==");
    log.flush();
    log.close();

  }
  catch (IOException e)
  {
     e.printStackTrace();
  }
}
}