StringBuilder

package dynamic;

import java.io.DataInputStream;
import java.io.InputStream;
import java.util.Scanner;

/**
 * Created by yuan on 2017/2/16.
 */
public class testStrem

    public static void main(String[] args) {

        StringBuilder out = new StringBuilder();
        out.append("a");
        out.append("b");
        out.append("b");
        out.append("b");
        out.append("b");
        System.out.println(out.toString());
    }
}