【每日日报】第四十天 工具类
1 今天看网课
1）StingBuilder和StringJoiner
1 package liuer;
2 import java.util.StringJoiner;
3
4 public class StringBuilderDemo {
5 public static void main(String[] args){
6 StringBuilder sb=new StringBuilder();
7 sb.append(52);
8 sb.append(1).append("中国");
9 System.out.println(sb.toString());
10 int[] arr=new int[]{12,24,35,46};
11 StringJoiner sj=new StringJoiner(", ","[","]");
12 for(int x:arr){
13 sj.add(Integer.toString(x));
14 }
15 System.out.println(sj.toString());
16 }
17 }
2)Intege
1 package liuer;
2
3 public class IntegerDemo {
4 public static void main(String[] args){
5 Integer a=12;
6 System.out.print(a.valueOf(a));
7 }
8
9 }
3)Math
1 package liuer;
2 import java.util.Random;
3
4 public class MathDemo {
5 public static void main(String[] args){
6 Random random=new Random();
7 for(int i=0;i<10;i++){
8 System.out.println(random.nextInt(10));
9 }
10 }
11
12 }
2 没什么问题
3 明天继续看网课
