java - 如何在java的I/O流中转换c++的freopen

Question

当我在java中编码时，我必须读取一个文件并在java上写入

我有 C++ 代码

freopen("addin.txt","r",stdin); freopen("addin.txt","w",stdout);

我必须在java中转换这段代码我怎么能？

i have tried this in java.

int frw(){
File f1=new File("addin.txt","r");
File f2=new File("addout.txt","w");
FileInputStream fi=new FileInputStream(f1);
FileOutputStream fo=new FileOutputStream(f2);
a=s.nextInt(fi.read());    
b=s.nextInt(fi.read());   
fo.write(b);    
}

this is code in c++ which i to convert into java

int main()
{
freopen("addin.txt","r",stdin);
freopen("addout.txt","w",stdout); 
int a,b;
cin>>a>>b;
cout<<a+b;
return 0;
}

Answer 1

public class  Main {   
  static private  final String INPUT =  "input.txt" ;   
  static private  final String OUTPUT =  "output.txt" ;   

  public static void  main (String args []) {    
      // open I / O files  
      FileInputStream instream = null;  
      PrintStream outstream = null;  

      try  {  
          instream =  new  FileInputStream (INPUT);  
          outstream =  new  PrintStream ( new  FileOutputStream (OUTPUT));  
          System.setIn (instream);  
          System.setOut (outstream);  
      }  catch  (Exception e) {  
          System.err.println ( "Error Occurred." );  
      }  

      Scanner in =  new  Scanner (System.in); 
      int a =  in.nextInt ();  
      int b =  in.nextInt ();
      System.out.println (a+b);

  }  

}