package com.learningjava;

/**
 * This programe try to illuminate UTF-16 in java
 * 
 * for unicode character refer to the following website :
 * http://www.scarfboy.com/coding/unicode-tool?
 * 
 * for more details refer to the book 《core java : volume 1》
 * 
 * for utf-16 algorithm refer to the following website :
 * http://en.wikipedia.org/wiki/UTF-16#Example_UTF-16_encoding_procedure
 * 
 * @author  wangdq
 * 2013-09-26
 */

public class UTF16Test {
	public static void main(String[] args) {
		  String sample = null;
		  if(args.length > 0) {
			  sample = args[0];
		  } else {
			  // for the sake of not show the character of u+1D56B
			  String special = new String(Character.toChars(0x1D56B));
			  sample = special+" zZ";
		  }
		  System.out.println("sample string is:  "+sample);
		  
		  // String.length : Returns the length of this string.
		  // The length is equal to the number of Unicode code units in the string.
		  int len = sample.length();
		  System.out.println("code units count:  "+len);
		  // traverse the string by code units
		  System.out.print("code units are:  ");
		  UTF16Test.traverseByCodeUnits(sample);
		  System.out.println();
		  
		  
		  // get the number of Unicode code points
		  int cpCount = sample.codePointCount(0, len);
		  System.out.println("code points count:  "+cpCount);
		  
		  // traverse the string by code point s
		  System.out.print("code points are:  ");
		  UTF16Test.traverseByCodePoints(sample);
		  System.out.println();
		 
	}
	/**
	 * traverse the string by code points
	 * @param str the specified string to traverse
	 */
	public static void traverseByCodePoints(String str) {
		int cpCount = str.codePointCount(0, str.length());
		 for(int ix = 0;ix < cpCount;ix++) {
			 printCodePoint(str.codePointAt(ix));
		 }
	}
	/**
	 * traverse the string by code units
	 * @param str the specified string to traverse
	 */
	public static void traverseByCodeUnits(String str) {
		int cuCount = str.length();
		for(int ix = 0;ix < cuCount;ix++) {
			String content = String.format("(%04x)  ",
					(int)str.charAt(ix)).toUpperCase();
			System.out.print(content);//get code unit
		}
		
	}
	/**
	 * print code point in hexadecimal form
	 * @param cp the code point
	 */
	private static void printCodePoint(int cp) {
		
		//check if is the supplementary code point
		if(Character.isSupplementaryCodePoint(cp)) {
			char[] chs = Character.toChars(cp);//stored the code point in  UTF-16 representation
			String content = String.format("[U+%04x,U+%04x]  ",
					(int)chs[0],(int)chs[1]).toUpperCase();
			System.out.print(content);
		} else {
			String content = String.format("[U+%04x]  ",cp).toUpperCase();
			System.out.print(content);
		}
	}
}