StringBuilder

public class demo11 {
    public static void main(String[] args) {
        //StringBuilder可以看作为一个容器，创建之后里面内容可变
        //1.创建对象

        StringBuilder sb = new StringBuilder();
        //StringBuilder sb = new StringBuilder("abc");

        //2.添加元素
        sb.append("abc");
        sb.append("ABC");
        sb.append("软萌小鲨鱼");


        //3.反转
        sb.reverse();
        System.out.println(sb);

        //获取长度
        int lenth = sb.length();
        System.out.println(lenth);

        //变回字符串
        String str = sb.toString();
        System.out.println(str);


    }
}

public class demo12 {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder();
        sb.append("aaa").append("bbb").append("ccc");
        System.out.println(sb);
    }
}