How do I get a part or a substring of a string?

package org.kodejava.example.lang;

public class SubstringExample {
    public static void main(String[] args) {
        // This program demonstrate how we can take some part of a string 
        // or the what we called as substring. Java String class provides 
        // substring method with some overloaded parameter.

        String sentence = "Lorem ipsum dolor sit amet...";

        // The first substring method with single parameter beginIndex 
        // will take some part of the string from the beginning index 
        // until the last character in the string.
        String part = sentence.substring(6);
        System.out.println("Part of sentence: " + part);

        // The second substring method take two parameters, beginIndex 
        // and endIndex. This method returns the substring start from 
        // beginIndex to the endIndex.
        part = sentence.substring(12, 21);
        System.out.println("Part of sentence: " + part);