What is the difference between static methods and non-static methods in java

Difference: 1. Static methods are methods modified with the static keyword and belong to classes, not objects; non-static methods are ordinary methods that are not modified with the static keyword, belonging to objects but not classes. 2. Static methods can be called directly, class name calls and object calls; non-static methods can only be called through objects. 3. Different life cycles.

The operating environment of this tutorial: windows7 system, java8 version, DELL G3 computer.

1. The difference between static methods and non-static methods (calling objects and reference variables are different)

Static method: It is a method modified with the static keyword, also called Class method. It belongs to the class, not to the object. You can call the static method through the class name and method name before instantiating the object. (Static attributes and static methods belong to classes and can be called directly through the class name).

A. In a static method, you can call a static method.

B. In a static method, non-static methods cannot be called.

C. In a static method, you can reference class variables (that is, variables modified by static).

D. In a static method, member variables cannot be referenced (that is, variables without static modification).

E. In static methods, the super and this keywords cannot be used

Non-static method: It is an ordinary method that does not contain the static keyword modification, also known as instance method and member method. Belongs to objects, not to classes. (Member attributes and member methods belong to the object, and the object must be created through the new keyword and then called through the object).

A. In ordinary methods, ordinary methods can be called.

B. In ordinary methods, you can call static methods

C. In ordinary methods, you can reference class variables and member variables

D. In ordinary methods, You can use the super and this keywords

2. The difference between static methods and non-static methods (different calling methods)

Static methods can be called directly, and the class name call and Object call. (Class name. Method name / Object name. Method name)

But non-static methods can only be called through objects. (Object name. Method name)

3. The difference between static methods and non-static methods (different life cycles)

The life cycle of a static method is the same as that of the corresponding class Long, static methods and static variables are allocated and loaded into memory as the class is defined. Static properties and methods will not be destroyed until the thread ends. (That is, static methods belong to classes)

The life cycle of non-static methods is as long as the instantiated object of the class. Only when the class instantiates an object, the non-static method will be created, and when this object When destroyed, non-static methods are also destroyed immediately. (That is, non-static methods belong to objects)

Summary: Class methods can be called directly through the class name, instance methods must first instantiate the class, then initialize the object, and then call it through the instance object of the class

Example:

class XYZ{
public static void main(String[] str){
     XYZ.testStatic();         //直接通过类调用

     XYZ a = new XYZ();        //实例化，然后构造方法会初始化
     a.testMethod();           //对象调用方法
}

public static void testStatic(){
System.out.println("This is static method");
}

public void testMethod(){
System.out.println("This is instance method");
}
}

Static static variables/methods are initialized during the class loading process, and there is only one copy in the memory, so it can be regarded as a global variable/method.

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