StackOverflow - Q33467878 - MCVE by TheLima

Main.java

/*
If you get "END!" without any results, we have a problem.
My result is:
"2567
2576
END!"
 */
package Q_33467878;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 *
 * @author Rodrigo Legendre Lima Rodrigues (AlmightyR) <rodrigolegendre.com>;
 */
public class Main {

  /**
   * @param args the command line arguments
   */
  public static void main(String[] args) {
    String test = "{\"company_id\":2567\"IDNUmber=8847,school:Seen\"company_id\":2576\"}";

    Pattern pattern = Pattern.compile("(?<=company_id\\\\\":)\\d{4}");
    Matcher matcher = pattern.matcher(test);

    while (matcher.find()) {
      System.out.println(matcher.group());
    }
    System.out.println("END!");
  }
}