迷失北京

package test;
import org.apache.commons.lang.StringUtils;
public class CutString {
	//性能最差
	public String testPlus() {
		String s = "";
		for (int i = 0; i < 10000; i++) {
			s = s + String.valueOf(i);
		}
		return s;
	}
	//較好
	public String testConcat() {
		String s = "";
		for (int i = 0; i < 10000; i++) {
			s = s.concat(String.valueOf(i));
		}
		return s;
	}
	
	//性能與testStringBuffer相差無幾，比其要好
	public String testJoin() {
		String[] list = new String[10000];
		for (int i = 0; i < 10000; i++) {
			list[i] = String.valueOf(i);
		}
		return StringUtils.join(list, "");
	}
	public String testStringBuffer() {
		StringBuffer sb = new StringBuffer();
		long l1 = System.currentTimeMillis();
		for (int i = 0; i < 10000; i++) {
			sb.append(String.valueOf(i));
		}
		long l2 = System.currentTimeMillis();
		System.out.println(l2-l1);
		return sb.toString();
	}
	
	//性能最高的方法
	public void testStringBuilder() {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < 100000; i++) {
			sb.append(String.valueOf(i));
		}
		sb.toString();
	}
	public static void main(String[] args) {
		System.out.println(new CutString().testStringBuffer());
	}
}