[20160730]while 条件的死循环和正常循环对比

正常循环

 1 import java.io.*;
 2 import java.util.*;
 3
 4 public class MyPrintStreamTest3{
 5   public static void main(String[] args) {
 6     BufferedReader br = new BufferedReader(  new InputStreamReader(System.in) );
 7     String s = null;
 8
 9   try
10   {
11     PrintWriter log = new PrintWriter( new FileWriter("D://javalearning//MYIO//log4j.txt",true) );
12     while((s = br.readLine())!=null){
13       if (s.equalsIgnoreCase("exit")) break;
14        System.out.println(s.toUpperCase());
15        log.println("--------");
16        log.println(s.toUpperCase());
17        log.flush();
18     }
19     log.println("=="+new Date()+"==");
20     log.flush();
21     log.close();
22
23   }
24   catch (IOException e)
25   {
26      e.printStackTrace();
27   }
28 }
29 }

死循环

 1 import java.io.*;
 2 import java.util.*;
 3
 4 public class MyPrintStreamTest3{
 5   public static void main(String[] args) {
 6     BufferedReader br = new BufferedReader(  new InputStreamReader(System.in) );
 7     String s = null;
 8
 9   try
10   {
11     PrintWriter log = new PrintWriter( new FileWriter("D://javalearning//MYIO//log4j.txt",true) );
12     s = br.readLine();
13     while(s!=null){
14       if (s.equalsIgnoreCase("exit")) break;
15        System.out.println(s.toUpperCase());
16        log.println("--------");
17        log.println(s.toUpperCase());
18        log.flush();
19     }
20     log.println("=="+new Date()+"==");
21     log.flush();
22     log.close();
23
24   }
25   catch (IOException e)
26   {
27      e.printStackTrace();
28   }
29 }
30 }