使用if語句

Question

我是Java初學者，我正在學習if語句沒有else，請問社區檢查我的代碼是否改進？

問題陳述： 在這段代碼中，我們只使用if語句來練習。在這裏你需要輸入你的年齡才能進入酒吧與熱辣女孩，如果你的年齡在18歲以上，你可以進入。 如果它低於18你不能進入。

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

你的代碼是，除了最後的精if語句應該比不僅僅是少，不等於以下，所有的如果最後兩個前語句是多餘的，所以你可以將它們刪除。你只需要考慮兩種可能性：18歲以上的人，或者18歲以下的人。

Answer 2

你的代碼將會'工作'，因爲它會打印每個年齡輸入的註釋。但是，因爲您不使用其他或嵌套，它總是會產生多個註釋。例如：如果輸入17，則將觸發對於<> 18,< 18和< = 18的評論。對於18的特定輸入，其中一個打印的評論將與其他評論相沖突，因爲= 18和> = 18條評論會讓你進入，而< = 18條評論會拒絕你的輸入。

Answer 3

如果您只需要使用'if'，它在代碼中的使用是正確的，但是您的條件正在重複。 提示：如果一個人的年齡應該是20，那麼您的代碼的第二，第三和第五個條件將爲真，並且所有這些都將輸出。正如你在問題中所說的，你需要檢查年齡是大於還是小於18，並且如果你想檢查它是否等於18，那麼從所有這些條件中，你只需要兩個

Answer 4

從技術上講，你剛纔案件：

• age < 18
• age == 18
• age > 18

所以，你可以簡化你的代碼

... 
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"); 
} 

如果你想確保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"); 
}