Java 返回一个值。输出总是打印0

我正在学习如何返回一个值并尝试编写以下代码

public class JustTryingReturn {

static int a, b;
static Scanner sc = new Scanner(System.in);
static int nganu() {
return a+b;
}

public static void main(String[] args) {
    int c = nganu();
    System.out.println("Enter number ");
    a = sc.nextInt();
    b = sc.nextInt();
    System.out.println(c);
}

}

但是输出总是打印0，而不是

a+b

。我做错了什么？

---

谢谢。

你应该打这个电话

int c = nganu();

分配

a

和

b

的输入值后。否则，在计算它们的总和时，默认情况下它们仍将包含

0

System.out.println("Enter number ");
a = sc.nextInt();
b = sc.nextInt();
int c = nganu();
System.out.println(c);

---

你应该打电话

int c = nganu();

分配

a

和

b

的输入值后。否则，在计算它们的总和时，默认情况下它们仍将包含

0

System.out.println("Enter number ");
a = sc.nextInt();
b = sc.nextInt();
int c = nganu();
System.out.println(c);

---

为

a

和

b

赋值后，必须调用函数
那么就这样说：

intc=nganu（）在您获得
a
和
b
之后
 为
a
和
b
赋值后，必须调用函数
那么就这样说：
intc=nganu（）在您获得
a
和
b
之后
 请相应地更改您的代码，

public static void main(String[] args) {
    //int c = nganu(); // here first time a,b is 0, still you haven't assign...
    System.out.println("Enter number ");
    a = sc.nextInt(); // now, actually you have assign value to a
    b = sc.nextInt(); // now, actually you have assign value to b
    int c = nganu();
    System.out.println(c);
}

请相应地更改您的代码，

public static void main(String[] args) {
    //int c = nganu(); // here first time a,b is 0, still you haven't assign...
    System.out.println("Enter number ");
    a = sc.nextInt(); // now, actually you have assign value to a
    b = sc.nextInt(); // now, actually you have assign value to b
    int c = nganu();
    System.out.println(c);
}

尝试使用这一行的顺序更改：

 int c = nganu();
 a = sc.nextInt();
 b = sc.nextInt();

像这样：

 public class JustTryingReturn {
  static    int a, b;

 static Scanner sc = new Scanner(System.in);
 static  int nganu() {
 return a+b;
}

 public static void main(String[] args) {

  // the order was changed
   System.out.println("Enter number ");
    a = sc.nextInt();  
    b = sc.nextInt();   
   int c = nganu();
System.out.println(c);
 }  

  }

尝试使用这一行的顺序更改：

 int c = nganu();
 a = sc.nextInt();
 b = sc.nextInt();

像这样：

 public class JustTryingReturn {
  static    int a, b;

 static Scanner sc = new Scanner(System.in);
 static  int nganu() {
 return a+b;
}

 public static void main(String[] args) {

  // the order was changed
   System.out.println("Enter number ");
    a = sc.nextInt();  
    b = sc.nextInt();   
   int c = nganu();
System.out.println(c);
 }  

  }