// strings/JGrep.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// A very simple version of the "grep" program
// {java JGrep
// WhitherStringBuilder.java 'return|for|String'}
import java.util.regex.*;
import java.nio.file.*;
import java.util.stream.*;

public class JGrep {
 public static void
 main(String[] args) throws Exception {
 if(args.length < 2) {
 System.out.println(
 "Usage: java JGrep file regex");
 System.exit(0);
 }
 Pattern p = Pattern.compile(args[1]);
 // Iterate through the lines of the input file:
 int index = 0;
 Matcher m = p.matcher("");
 for(String line :
 Files.readAllLines(Paths.get(args[0]))) {
 m.reset(line);
 while(m.find())
 System.out.println(index++ + ": " +
 m.group() + ": " + m.start());
 }
 }
}
/* Output:
0: for: 4
1: for: 4
*/