StringBuolder

StringBuolder可以修改的字符串

创建StringBuilder k=new StringBuilder("可以在里面添加初值");

添加与反转

StringBuilder a=k.append("添加内容");

StringBuilder a=k.reverse();

a和k都是修改之后的结果

StringBuolder与String相互转换

package heima;

import javax.sound.sampled.Line;
import java.util.Scanner;

public class a1 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        String line= sc.nextLine();
        String line1=myReverse(line);
String line2=fzsjb(line);
        System.out.println(line+line1+line2);
    }
    public static String myReverse(String s){
        StringBuilder sb=new StringBuilder(s);
        sb.reverse();
        String ss=sb.toString();
        return ss;
    }
    public static String fzsjb(String s){//反转升级版
    return new StringBuilder(s).reverse().toString();
    }

}

package heima;
import java.util.Scanner;
public class ss {
    public static void main(String[] argc) {
int []arr={1,2,3};
String s=arrayToString(arr);
System.out.println("s"+s);
        }
public static String arrayToString(int[] arr){
    StringBuilder sb=new StringBuilder();
    sb.append("[");
    for(int i=0;i