使用if语句

Question

我是Java初学者，我正在学习if语句没有else，请问社区检查我的代码是否改进？

问题陈述： 在这段代码中，我们只使用if语句来练习。在这里你需要输入你的年龄才能进入酒吧与热辣女孩，如果你的年龄在18岁以上，你可以进入。 如果它低于18你不能进入。

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

你的代码是，除了最后的精if语句应该比不仅仅是少，不等于以下，所有的如果最后两个前语句是多余的，所以你可以将它们删除。你只需要考虑两种可能性：18岁以上的人，或者18岁以下的人。

Answer 2

你的代码将会'工作'，因为它会打印每个年龄输入的注释。但是，因为您不使用其他或嵌套，它总是会产生多个注释。例如：如果输入17，则将触发对于<> 18,< 18和< = 18的评论。对于18的特定输入，其中一个打印的评论将与其他评论相冲突，因为= 18和> = 18条评论会让你进入，而< = 18条评论会拒绝你的输入。

Answer 3

如果您只需要使用'if'，它在代码中的使用是正确的，但是您的条件正在重复。 提示：如果一个人的年龄应该是20，那么您的代码的第二，第三和第五个条件将为真，并且所有这些都将输出。正如你在问题中所说的，你需要检查年龄是大于还是小于18，并且如果你想检查它是否等于18，那么从所有这些条件中，你只需要两个

Answer 4

从技术上讲，你刚才案件：

• age < 18
• age == 18
• age > 18

所以，你可以简化你的代码

... 
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"); 
} 

如果你想确保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"); 
}