String_project/StringBuilder_module/src/StringBuilder_package/StringBuilder_demo2.java

package StringBuilder_package;

public class StringBuilder_demo2 {
    public static void main(String[] args) {
        //1、创建对象
        StringBuilder sb=new StringBuilder();

        //2、添加字符串
        sb.append("aaa").append("bbb").append("ccc").append("ddd");

        System.out.println(sb);

        //3、再把StringBuilder变回字符串
        String str=sb.toString();

        System.out.println(str);
    }
}