package Chapter8;

import java.io.*;
import java.util.*;

public class ReplaceText {
 public static void main(String[] args) throws Exception {
 // Check command line parameter usage
 if (args.length != 4) {
 System.out.println(
 "Usage: java ReplaceText sourceFile targetFile oldStr newStr");
 System.exit(0);
 }

 // Check if source file exists
 File sourceFile = new File(args[0]);
 if (!sourceFile.exists()) {
 System.out.println("Source file " + args[0] + " does not exist");
 System.exit(0);
 }

 // Check if target file exists
 File targetFile = new File(args[1]);
 if (targetFile.exists()) {
 System.out.println("Target file " + args[1] + " already exists");
 System.exit(0);
 }

 // Create input and output files
 Scanner input = new Scanner(sourceFile);
 PrintWriter output = new PrintWriter(targetFile);

 while (input.hasNext()) {
 String s1 = input.nextLine();
 String s2 = s1.replaceAll(args[2], args[3]);
 output.println(s2);
 }

 input.close();
 output.close();
 }
}