五种拼字条串方法

引用：http://www.cnblogs.com/focusj/archive/2011/02/16/2057630.html

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;
    }
    //较好
    public String testConcat() {
        String s = "" ;
        for ( int i = 0 ; i < 10000 ; i++) {
            s = s.concat(String.valueOf(i));
        }
        return s;
    }

    //性能与testStringBuffer相差无几，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());
    }
}