reduce byte length of a String (and its useless optimization)

StringReduceTest.java

public class StringReduceTest {
	private static final Charset UTF8 = Charset.forName("UTF-8");
	
	public String reduceStringUTF8Size(String s, int size) {
		while(s.getBytes(UTF8).length >size){
				s=s.substring(0,s.length()-1);
		}
		return s;
	}
	public String reduceStringUTF8Size2(String s, int size) throws CharacterCodingException {
		int newsize=0;
		int length = s.length();
		CharsetEncoder ce = UTF8.newEncoder();
		int pos = 0;
		for(int i=0; i<length;i++){
			char[] c= {s.charAt(i)};
			newsize += ce.encode(CharBuffer.wrap(c)).limit();
			if(newsize>size) {
				break;
			}
			pos = i;
		}
		return s.substring(0, pos + 1);
	}
	
	@Test
	public void monTest() throws UnsupportedEncodingException, CharacterCodingException{
		String s10 = "éèç@à$¤%ùµ";
//		String s10 = "éèç@à$¤%ùµ";
		Assert.assertEquals(s10.length(),10);
		String s200=s10+s10+s10+s10+s10+s10+s10+s10+s10+s10;
		s200 += s200;
		Assert.assertEquals(s200.length(),200);
		System.out.println(s200.getBytes("UTF-8").length);
		System.out.println(s200.getBytes("ISO8859_1").length);
		String s200bytes = null;
		long start = System.currentTimeMillis();
		for (int i = 0; i < 1000; i++) {
			s200bytes=reduceStringUTF8Size(s200,200);
		}
		long v1 = System.currentTimeMillis() - start;
		System.out.println(s200bytes.getBytes("UTF-8").length);
		System.out.println(s200bytes);
		System.out.println(s200bytes.length());
		Assert.assertEquals(s200bytes.getBytes("UTF-8").length,200);
		start = System.currentTimeMillis();
		for (int i = 0; i < 1000; i++) {
			s200bytes=reduceStringUTF8Size2(s200,200);
		}
		long v2 = System.currentTimeMillis() - start;
		System.out.println(s200bytes.getBytes("UTF-8").length);
		System.out.println(s200bytes);
		System.out.println(s200bytes.length());
		Assert.assertEquals(s200bytes.getBytes("UTF-8").length,200);
		System.out.println("v1 = " + v1 + ", v2 = " + v2);
	}

}