java自学笔记-day5

目录

API的使用

Scanner类&& anonymous object

Random类

笔记基于

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API的使用

API(Application Programming Interface),应用程序编程接口

Overview (Java Platform SE 8 ) (oracle.com)

一、Scanner类，属于java.util包，constr构造，method方法

除java.long下的类，其余包下的都要写导包语句

import java.util.Scanner;

 二、点击constr查看构造方法

Scanner sc = new Scanner(Sytems.in);        System.in代表键盘输入，此处作参数

 三、查看方法使用

 String str = sc.next();

 int num = sc.nextInt();

两个练习，查阅API

Scanner类&& anonymous object

import java.util.Scanner;

public class ScannerDemo {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);    //new一个名为sc的实例
        int num1 = sc.nextInt();
        int num2 = sc.nextInt();
        int ret = num1 < num2 ? num2:num1;      //三元表达式
        System.out.println("max = "+ret);

        String name = sc.next();
        System.out.println(name + " has been recorded.");

        String name2 = new Scanner(System.in).next();   //这里new的就是一个匿名对象,直接调用                 
        System.out.println(name2 + " had launch.");     //这个对象使用成员方法.next()
                                                        //匿名对象只可调用一次，因为没有名字                                                                                
                                                        //给你调用
    }
}

output：        绿色为输入

54                
44
max = 54
hacker
hacker has been recorded.
defender
defender had launch.

Random类

import java.util.Random;

public class RandomDemo {
    public static void main(String[] args) {
        Random ra = new Random();
        for (int i = 1; i < 4; i++) {    //一个骰子摇三次
            int num = ra.nextInt(6)+1;   
            System.out.println(num +"\t"+i);
        }
    }
}
output：
6	1
6	2
6	3

笔记基于

Java基础+进阶_哔哩哔哩_bilibili正在上传…重新上传取消​https://www.bilibili.com/video/BV1uJ411k7wy不足与错误之处，敬请指正。