public class Str
{
	public static void main(String args[])
	{
		String s = "abcdefghijk";

		//substring
		System.out.println(s.substring(0, 2));

		//concat
		String s2 = "lmnopqrst";
		System.out.println(s.concat(s2));
		System.out.println(s+s2);

		//format
		String s3;
		s3 = String.format("Year: %d", 2017);
		System.out.println(s3);

		//float to string
		String s4 = String.valueOf(3.14);
		System.out.println(s4);

		//string to float
		float f = Float.valueOf("3.14");
		System.out.println(f);

		//split
		s = "575-571-0350";
		String [] array = s.split("-");
		for(int i = 0; i < array.length; i++)
			System.out.println(array[i]);

		//replace
		System.out.println(s.replace('-', '.'));

		//equals, ==
		if(s.equals("575.571.0350"))
			System.out.println("Equals");
		else
			System.out.println("Not Equals");

		if(s == "575.571.0350")
			System.out.println("==");
		else
			System.out.println("!=");
	}
}
			

• equals(), test equality of two objects
• ==, compare reference, whether they are the same object

• String is immutable, StringBuilder is mutable

public class Str
{
	public static void main(String args[])
	{
		//String is immutable
		String s = "Hello";

		System.out.println(System.identityHashCode(s));

		s = "World!";
		System.out.println(System.identityHashCode(s));

		//s[0] = 'H'; // not able to change a character

		//StringBuilder is mutable
		StringBuilder sb = new StringBuilder("Hello World!");

		//append
		sb.append(3.14);
		System.out.println(sb);

		//insert
		sb.insert(0, 3.14);
		System.out.println(sb);

		//delete
		sb.delete(0, 4);
		System.out.println(sb);

		//replace
		sb.replace(0, 1, "Hello");
		System.out.println(sb);

		//reverse
		System.out.println(sb.reverse());
	}
}
			

import java.util.StringTokenizer;

public class Token
{
	public static void main(String args[])
	{
		StringTokenizer t = new StringTokenizer("1, 2, 3, 4", ", ");//multiple delimiters

		System.out.printf("Number of Tokens: %d%n", t.countTokens());

		while(t.hasMoreTokens())
		{
			System.out.println(t.nextToken());
		}
	}
}
			

public class Reg
{
	public static boolean validPhoneNumber(String s)
	{
		return s.matches("\\d{3}[=.]\\d{3}[-.]\\d{4}");
	}

	public static void main(String args[])
	{
		String phoneNumber = "575.571.0350";

		System.out.println(validPhoneNumber(phoneNumber));
	}
}
			

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

public class Reg
{
	public static void main(String args[])
	{
		Pattern p = Pattern.compile("\\d{3}[-.]\\d{3}[-.]\\d{4}");
		String s = "575.571.0350, 575.571.1583";

		//Pattern
		System.out.println(Pattern.matches("\\d{3}[-.]\\d{3}[-.]\\d{4}.*", s));
		System.out.println(Pattern.quote(s));

		//Matcher
		Matcher m = p.matcher(s);
		while(m.find())
		{
			System.out.println(m.group());
		}
	}
}
			

• BreakIterator, natural text language
• StreamTokenizer, programming language

import java.util.*;
import java.text.*;

public class S
{
	public static void main(String args[])
	{
		Locale currentLocale = new Locale ("en","US");

		BreakIterator itr = BreakIterator.getWordInstance(currentLocale);

		itr.setText("Hello Lin, how is everything going?");

		//get the start and end of each word
		int boundary = itr.first();

		while(boundary != BreakIterator.DONE)
		{
			System.out.println(boundary);
			boundary = itr.next();
		}
	}
}