public class StringClasses {

	public static void main(String[] args) {
		String str = buildstring();
		System.out.println(str);
		strreverse(str);
		sbreverse(str);
		strbuffer(str);
		strbuilder(str);
		strbuilderreverse(str);


	}
	public static String buildstring(){
		String str = "";
		int size = 16536;
		char ch = 'a';
		Long beginTime = System.currentTimeMillis();
		for (int count = 0; count < size; ++count) {
			str += ch;
			++ch;
			if (ch > 'z') {
				ch = 'a';
			}
		}
		Long elapsedTime = System.currentTimeMillis() - beginTime;
		System.out.println("elapsed time is " + elapsedTime + "ms (build string)" );
		return str;
	}
	//a
	public static void strreverse(String s) {
		Long beginTime = System.currentTimeMillis();
		String reversestr = "";
		for (int i = s.length() - 1; i>=0; i--) {
			reversestr += s.charAt(i);
		}
		Long elapsedTime = System.currentTimeMillis() - beginTime;
		System.out.println("elapsed time is " + elapsedTime + "ms (using string to reverse)" );
		//System.out.println(reversestr);
	}
	//b
	public static void sbreverse(String s) {
		Long beginTime = System.currentTimeMillis();
		StringBuffer sb= new StringBuffer();

		for (int i = s.length() - 1; i>=0; i--) {
			sb.append(s.charAt(i));
			}
		Long elapsedTime = System.currentTimeMillis() - beginTime;
		System.out.println("elapsed time is " + elapsedTime + "ms (using stringbuffer to reverse)" );
		//System.out.println(sb);
		}
	//c
	public static void strbuffer(String s) {
		Long beginTime = System.currentTimeMillis();
		StringBuffer buffer = new StringBuffer(s);
	    buffer.reverse();
	    Long elapsedTime = System.currentTimeMillis() - beginTime;
		System.out.println("elapsed time is " + elapsedTime + "ms (using stringbuffer's reverse() method)" );
		//System.out.println(buffer);
	}
	//d
	public static void strbuilder(String s) {
		Long beginTime = System.currentTimeMillis();
		StringBuilder sb= new StringBuilder();
		for (int i = s.length() - 1; i>=0; i--) {
			sb.append(s.charAt(i));
			}
		Long elapsedTime = System.currentTimeMillis() - beginTime;
		System.out.println("elapsed time is " + elapsedTime + "ms (using stringbuilder to reverse)" );
		//System.out.println(sb);
	}
	//e
	public static void strbuilderreverse(String s) {
		Long beginTime = System.currentTimeMillis();
		StringBuilder sb= new StringBuilder(s);
		sb.reverse();
		Long elapsedTime = System.currentTimeMillis() - beginTime;
		System.out.println("elapsed time is " + elapsedTime + "ms (using stringbuilder's reverse() method)" );
		//System.out.println(sb);
	}

	}