js也行。
网上有类似的在线对比工具,大概就是这种效果。

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
public class Demo {
public static void main(String[] args) throws IOException {
BufferedReader b1 = new BufferedReader(new FileReader("F:\a.txt"));
BufferedReader b2 = new BufferedReader(new FileReader("F:\b.txt"));
BufferedWriter bw = new BufferedWriter(new FileWriter("F:\ab.txt"));
String s1 = null;
String s2 = null;
ArrayList list1 = new ArrayList();
ArrayList list2 = new ArrayList();
while((s1=b1.readLine())!=null){
list1.add(s1);
}
while((s2=b2.readLine())!=null){
list2.add(s2);
}
list1.removeAll(list2);
for(Iterator it = list1.iterator(); it.hasNext();){
bw.write(it.next()+"\r\n");
}
bw.close();
b2.close();
b1.close();
}
}