java - if语句的使用

Question

我是 Java 初学者，正在学习 if 语句没有 else，请社区检查我的代码以改进？

问题陈述:在这段代码中我们只使用 if 语句来练习。这里需要输入年龄才能进入有辣妹的酒吧，如果你的年龄在18岁以上就可以进入。 如果低于 18 岁，则不能进入。

import java.util.Scanner;

public class Main {
    public static void main(String[] args){

        Scanner input = new Scanner(System.in);

        int age;

        // Ask the age
        System.out.println("Please write your age to enter to the bar:");
        age = input.nextInt();

        // Equal to
        if(age == 18){
            System.out.println("Your age " + age + " it's equal to 18, you can enter");
        }

        // Not equal to
        if(age != 18){
            System.out.println("Your age " + age + " it's not equal to 18");
        }

        // Greater than
        if(age > 18){
            System.out.println("Your age " + age +  " " + "is greater than 18, you can enter");
        }

        // Less than
        if(age < 18){
            System.out.println("Your age " + age + " " + "is less than 18, you can't enter");
        }

        // Greater than or equal to
        if(age >= 18){
            System.out.println("Your age " + age + " is greater than or equal to 18, you can enter");
        }
        // Less than or equal to
        if(age <= 18){
            System.out.println("Your age " + age + " is less than or equal to 18, you can't enter");
        }
    }
}

Answer 1

从技术上讲，您只有 三种 情况:

• age < 18
• age == 18
• age > 18

所以你可以把你的代码简化成

...
if (age < 18) {
  System.out.println("Your age " + age + " it's not equal to 18");
  System.out.println("Your age " + age + " is less than 18, you can't enter");
  System.out.println("Your age " + age + " is less than or equal to 18, you can't enter");
}

// "else if" instead of "if" will make the code more readable   
if (age == 18) {
  System.out.println("Your age " + age + " it's equal to 18, you can enter");
  System.out.println("Your age " + age + " is greater than or equal to 18, you can enter"); 
  System.out.println("Your age " + age + " is less than or equal to 18, you can't enter");
}   

// "else" instead of "if" will make the code more readable   
if (age > 18) {
  System.out.println("Your age " + age + " it's not equal to 18");
  System.out.println("Your age " + age + " is greater than 18, you can enter");
  System.out.println("Your age " + age + " is greater than or equal to 18, you can enter");
} 

如果您想确保age >= 18 :

if (age >= 18) {
  System.out.println("Your age " + age + " is greater than or equal to 18, you can enter");
}

// "else" is a better choice here
if (age < 18) {
  System.out.println("Your age " + age + " is less than 18, you can't enter");  
}