java 输入问题 - Java / Java SE

怎么用Scaner从键盘输入多行数据...然后一起输出.....
  BufferedWriter f = null;
boolean a = false;
try {
f = new BufferedWriter(new FileWriter("D:/file.text"));
while (!a){
Scanner reader = new Scanner(System.in);
String s1 = null;
s1 = reader.nextLine();
if(s1 == "exit") 
break;
f.write(s1);
}
问题出现在哪里;
  请指点!!!!!谢谢

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s1 == "exit"改为s1.equals("exit")

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if(s1=="exit")
你改成if("exit".equals(s1))
就对了。

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LS正解

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Java code:

BufferedWriter f = null;
boolean a = true;
try {
f = new BufferedWriter(new FileWriter("D:/file.text"));
while (a) {
Scanner reader = new Scanner(System.in);
String s1 = null;
s1 = reader.nextLine();
System.out.println(s1);
if (s1.equals("exit")){
a=false;
}
f.write(s1);
}
f.flush();
f.close();
} catch (IOException e) {
e.printStackTrace();
}

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一二楼都正确。
s1 =