Java Foundation Chapter eighth (invocation of static members, encapsulation)

One, the static member of the two kinds of calls.

1. Object. member variable = value;

Example: STU1. name = "Java";

2. Class name. Member mode; It can be called directly in this way without the need for new, and the Calling method can also (Student. Getnum ())

Example: Student. count++;

Note:

Static methods can only access static variables, and static can only access statics.

Non-static methods can access both static and non-static variables.

Example 1:class student{

static int count;

public int Getnum () {///non-static method can call a static variable or call a non-static variable

count++;

return count;

}

}

The main program call must be new to an object before it can be called (because the Getnum () method is non-static, so it is not shared, to be new out of the object, it can be called with an object)

Student stu1 = new Student ();

int count1 = Stu1.getnum ();

Example 2:class student{

static int count;

public static int Getnum () {

count++;

return count;

}

}

The main program calls int count2 = Student.getnum ();

Second, static block.

static{

}

Static blocks can only be loaded and run once, and executed first.

Example: Class student{

public static int count;

static{

count++;

}

public void Studentnum () {

System.out.println (count);

}

}

Main program Call: New Student (). Studentnum (); 1

New Student (). Studentnum (); 1

Three, encapsulation.

1. Encapsulate the function of the code:

Provide only a name to the outside world to allow access to these properties or functions.

2. Example: Bank security

Class creditcard{

private double salary; Outside access to the salary, it encapsulates

Public double getsalary () {

return salary;

}

public void Setsalary (double sal) {

if (Sal <= 0) {

return 0.0;

}else{

salary = sal;

}

return salary;

}

}

public class money{

public static void Main (string[] args) {

CreditCard cc = new CreditCard ();

Cc.setsalary (100000000);

Double salary = cc.getsalary ();

}

}

Note: Private privately, only own, outside access.

Java Foundation Chapter eighth (invocation of static members, encapsulation)