Java StringBuilder( )方法

String和StringBuilder的区别:
String:内容是不可变的

StringBuilder:内容是可变的

public StringBuilder( );创建一个空白可变字符串对象，不含任何内容

public StringBuilder( String str);根据字符串的内容，来创建可变字符串对象

public class Application {
    public static void main(String[] args) {
        StringBuilder sc = new StringBuilder();
        System.out.println(sc);
        System.out.println(sc.length());

        StringBuilder sc2 = new StringBuilder("mqs");
        System.out.println(sc2);
        System.out.println(sc2.length());
    }
}

 

public class Application {
    public static void main(String[] args) {
        StringBuilder sc = new StringBuilder();

        sc.append("mqs");
        System.out.println(sc);
        //链式编程
        sc.append("mqs1").append("mqs2");
        System.out.println(sc);
        sc.reverse();
        System.out.println(sc);
       }
}