1  import java.io.*;
  2  import java.util.*;
  3  
  4  public class ReplaceText {
  5    public static void main(String[] args) throws Exception {
  6      // Check command line parameter usage
  7      if (args.length != 4) {
  8        System.out.println(
  9          "Usage: java ReplaceText sourceFile targetFile oldStr newStr");
 10        System.exit(1);
 11      }
 12  
 13      // Check if source file exists
 14      File sourceFile = new File(args[0]);
 15      if (!sourceFile.exists()) {
 16        System.out.println("Source file " + args[0] + " does not exist");
 17        System.exit(2);
 18      }
 19  
 20      // Check if target file exists
 21      File targetFile = new File(args[1]);
 22      if (targetFile.exists()) {
 23        System.out.println("Target file " + args[1] + " already exists");
 24        System.exit(3);
 25      }
 26  
 27      try (
 28        // Create input and output files
 29        Scanner input = new Scanner(sourceFile);
 30        PrintWriter output = new PrintWriter(targetFile);
 31      ) {        
 32        while (input.hasNext()) {
 33          String s1 = input.nextLine();
 34          String s2 = s1.replaceAll(args[2], args[3]);
 35          output.println(s2);
 36        }
 37      }
 38    }
 39  }