對println的引用是模棱兩可的錯誤

Question

我有代碼一個非常基本的程序比當我輸入System.out.println時，我得到的錯誤：「引用println模糊」，隨機它使用工作，並沒有有一個錯誤，但現在它確實發生了這種錯誤，所以我如何解決這個問題，比你。

package blue.light; 
    //name is: slash 
    import java.util.*; 

    public class BlueLight { 

     public static void main(String[] args) throws InterruptedException { 
    Scanner scan = new Scanner(System.in); 

    String name; 
    int age; 
    String a; 
    String yes; 
    String no; 
    double num1; 
    double num2; 
    double ans; 





    System.out.println("hello, my name is Slash"); 
    System.out.println("What is your name?"); 
    name = scan.nextLine(); 
    System.out.println("Hello " + name); 
    Thread.sleep(1000); 
    System.out.println("How old are you?"); 
    age = scan.nextInt(); 
    if(age < 18) 
      { 
       System.out.println("ur young af"); 
      } 
    else if (age == 21) 
    { 
     System.out.println("Shots, shots, shots"); 

    } 
    else if (age == 69) 
    { 
     System.out.println("ohhh yea"); 
    } 
    System.out.println("you to calculate any thing?"); 
    a = scan.nextLine(); 
    if(a==("yes")){ 
     System.out.println("What would u like to do?(multiply,or add)");  
     a = scan.nextLine(); 
        if(a == "add"){ 
      System.out.println("Enter number 1"); 
      num1 = scan.nextDouble(); 
      System.out.println("Enter number 2"); 
      num2 = scan.nextDouble(); 
        ans = num1+num2; 

     } 


    } 

} 
    } 

Answer 1

首先，nextInt()歲以後不消耗新線（所以你nextLine然後空）。您將Object的值與致電.equals()的值進行比較，因爲==測試參考身份（並使用String我會使用String.equalsIgnoreCase(String)）。最後，我會在Java中聲明變量的最小可見性;儘可能接近他們的第一次使用。喜歡的東西，

public static void main(String[] args) throws InterruptedException { 
    Scanner scan = new Scanner(System.in); 

    System.out.println("hello, my name is Slash"); 
    System.out.println("What is your name?"); 
    String name = scan.nextLine(); 
    System.out.println("Hello " + name); 
    Thread.sleep(1000); 
    System.out.println("How old are you?"); 
    int age = scan.nextInt(); 
    if (age < 18) { 
     System.out.println("ur young af"); 
    } else if (age == 21) { 
     System.out.println("Shots, shots, shots"); 
    } else if (age == 69) { 
     System.out.println("ohhh yea"); 
    } 
    System.out.println("you to calculate any thing?"); 
    scan.nextLine(); // <-- nextInt leaves a trailing new line. 
    String a = scan.nextLine(); 
    if (a.equalsIgnoreCase("yes")) { // <-- compare string for equality in 
             // Java 
     System.out.println("What would u like to do?(multiply,or add)"); 
     a = scan.nextLine(); 
     if (a.equalsIgnoreCase("add")) {// <-- compare string for equality 
             // in Java 
      System.out.println("Enter number 1"); 
      double num1 = scan.nextDouble(); 
      System.out.println("Enter number 2"); 
      double num2 = scan.nextDouble(); 
      double ans = num1 + num2; 
      System.out.println(ans); // <-- display answer 
     } 
    } 
}