可变字符串StringBuffer和StringBuilder

  public static void main(String[] args) {
        StringBuilder  stringBuilder=new StringBuilder("123");
        stringBuilder.append(123);
        System.out.println(stringBuilder);
    }

public static void main(String[] args) {
        StringBuffer stringBuffer=new StringBuffer("wyb");
        stringBuffer.append(" I love you");
        System.out.println(stringBuffer);
    }