hi guys, i just start lernig exceptionc in java and it is still kinda confusing. this program was given in the book. right not i am just trying to revies program so that exceptions are handled in the main method by using the catch clause so need help with that.

this is java program

Thanks a lot

	* From Chapter 12 in Liang Y Daniel, Introduction to Java Programming, 11st Edition
	*/
	/**
	* the ReplaceText class demonstrates reading text from a file using Scanner
	* and writing text to a text file using PrintWriter
	*/
	import java.io.File;
	import java.io.PrintWriter;
	import java.util.Scanner;
	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(1);
	}
	// 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(2);
	}
	// 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(3);
	}
	try ( // try-with-resource to autoclose resources
	// 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);
	}
	}
	}
	}