Java示例替换第一次出现的字符串

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

public class Main {
   public static void main(String args[]) {
      Pattern p = Pattern.compile("hello");
      String instring = "hello hello hello.";
      System.out.println("initial String: "+ instring);
      Matcher m = p.matcher(instring);
      String tmp = m.replaceFirst("Java");
      System.out.println("String after replacing 1st Match: " +tmp);
   }
}