PTA字符串替换，总有一个点个不去

问题:

题目：
7-1 字符串替换 (10分)

将文本文件中指定的字符串替换成新字符串。 由于目前的OJ系统暂时不能支持用户读入文件，我们编写程序从键盘输入文件中的内容，当输入的一行为end时，表示结束。end后面有两个字符串，要求用第二个字符串替换文本中所有的第一个字符串。
输入格式:
Xi’an Institute of Posts and Telecommunications is co-designed and implemented by the People’s Government of Shaanxi Province and the Ministry of Industry and Information Technology. The Institute is located in Xi’an, a historic city in Northwest China, famous for its magnificent ancient culture.
end （表示结束）
Institute （第一个字符串，要求用第二个字符串替换）
University （第二个字符串）
输出格式:
Xi’an University of Posts and Telecommunications is co-designed and implemented by the People’s Government of Shaanxi Province and the Ministry of Industry and Information Technology.The University is located in Xi’an, a historic city in Northwest China, famous for its magnificent ancient culture.
输入样例:
Xi’an Institute of Posts and Telecommunications is co-designed and implemented by the People’s Government of Shaanxi Province and the Ministry of Industry and Information Technology.
The Institute is located in Xi’an, a historic city in Northwest China, famous for its magnificent ancient culture.
end
Institute
University

输出样例:
Xi’an University of Posts and Telecommunications is co-designed and implemented by the People’s Government of Shaanxi Province and the Ministry of Industry and Information Technology.The University is located in Xi’an, a historic city in Northwest China, famous for its magnificent ancient culture.
我的代码：
import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner in=new Scanner(System.in);
String string="";
while(in.hasNextLine()){
String s=in.nextLine();
if(s.equals("end")){
break;
}
else{
string=string+s;
}
}
String a=in.nextLine();
String b=in.nextLine();
System.out.println(string.replaceAll(a,b));
}
}

回答1:

自己测出来了，哈哈，开心，代码如下：
文本有换行的时候，去掉换行，中间也没有空格，上面的错误是这种情况多个空格
import java.util.Scanner;
public class Main{
public static void main(String[] args){
Scanner in=new Scanner(System.in);
String string="";
while(in.hasNextLine()){
String s=in.nextLine();
if(s.equals("end")){
break;
}
else{
string=string+s+"\n";
}
}
String a=in.nextLine();
String b=in.nextLine();
string.replaceAll("\n","");
System.out.print(string.replaceAll(a,b));
}
}