A simple comparison of the static keyword in C++ and Java

Static keyword is used for almost the same purpose in C and Java, but there are still some slight differences. The following article will take you through the similarities and differences of the static keyword in C and Java. I hope it will be helpful to you.

The similarities between C and the static keyword in Java

1. Static data Members:

In C and Java static data members are class members and are shared among all objects. For example, in the following Java program, static variable count is used to count the number of objects created.

class Test { 
    static int count = 0; 
  
    Test() {  
       count++;  
    }     
    public static void main(String arr[]) { 
       Test t1 = new Test(); 
       Test t2 = new Test(); 
       System.out.println("共创建了" + count + " 个对象");         
    } 
}

Output:

共创建了2个对象

2. Static member methods

Methods declared as static in C and Java are class members and have the following Restrictions:

1), they can only call other static methods. For example, fun() in the following program is non-static, but it is called in static main(), so the compilation fails.

class Main { 
    public static void main(String args[]) {    
        System.out.println(fun()); 
    }  
    int fun() { 
        return 20; 
    }  
}

2). Only static data must be accessed.

3), cannot access this or super. For example, the following program fails when compiling.

class Base { 
    static int x = 0;        
}    
  
class Derived extends Base  
{ 
   public static void fun() { 
       System.out.println(super.x); // 编译器错误：不能从静态上下文引用非静态变量
   }    
}

Note:

Both C and Java can access static data members and static methods without creating an object. They can be accessed using the class name. For example, in the following program, the static data member count and the static method fun() can be accessed without any object.

class Test { 
    static int count = 0; 
    public static void fun() {  
       System.out.println("调用了静态方法fun()");  
    }     
}    
       
class Main 
{ 
    public static void main(String arr[]) { 
       System.out.println("Test.count = " + Test.count);         
       Test.fun(); 
    } 
}

The difference between the static keyword in C and Java

##1. Static block

Unlike C, Java supports a special block called a static block (also called a static clause) that can be used for static initialization of a class; this code inside the static block is only executed once.

2. Static local variables

Unlike C, Java does not support static local variables. For example, the following Java program fails when compiling.

class Test { 
   public static void main(String args[]) {  
     System.out.println(fun()); 
   }  
   static int fun()  { 
     static int x= 10; //编译器错误：不允许静态局部变量
     return x--; 
   } 
}

Related video tutorial recommendations: "

Java Tutorial", "C Tutorial"

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