每日一鱼：每日一鱼之恶补Java

今日一🐟
StringBuilder and StringJoiner 以及 Enum

StringBuilder：
String是可变对象，可以预分配缓冲区，用来高效拼接字符串；
支持链式操作；

package com.company;

public class stringBuilder {
    public static void main(String[] args) {
        var sb = new StringBuilder(1024);
        sb.append("Mr ")
          .append("Bob")
          .append("!")
          .insert(0,"Hello,");
        System.out.println(sb.toString());
    }
}

StringJoiner：
StringJoiner 或String.join() 用来拼接字符串，还可以额外附加一个“开头”和结尾，

package com.company;

import java.util.StringJoiner;

public class stringJoiner {
    public static void main(String[] args) {
        var sb = new StringJoiner(",","hello ","!");
        String [] names = {"John","Uzi","Zoom"};
        for(String name : names){
            sb.add(name);
        }
        System.out.println(sb.toString());

    }
}

enum：
enum 适合在switch 语句中 ，
enum通过name（）获得定义字符串
可以为enum 编写构造方法

package com.company;

public class enum1 {
    public static void main(String[] args) {
        Weekday day = Weekday.SUN;
        System.out.println(day.name());
        if (day.dayValue == 6 || day.dayValue == 0) {
            System.out.println("work at home");
        }else {
            System.out.println("work at office");
        }
    }
}
enum Weekday {
    MON(1), TUE(2), WED(3), THU(4), FRI(5), SAT(6), SUN(0);

    public final int dayValue;

    private Weekday(int dayValue) {
        this.dayValue = dayValue;
    }
}

为了恶补JAVA ，特开启全新栏目《每日一🐟》，要天天坚持吧。
冲冲冲