First, two types of calls to static members.
1. object.member variable = value;
例：stu1 . name = "java";
2. Class name. Member method; // You can directly call in this way without new, and you can also call the method (Student . getNum())
例：Student .count++;
Note:
Static methods can only access static variables, and static can only access static.
Non-static methods can access both static and non-static variables.
例1：class Student{
static int count;
public int getNum(){ //Non-static methods can call both static variables and non-static variables
count++;
return count;
}
}
The main program call must first create an object before it can be called (because the getNum() method is non-static, it is not shared, and the object can be called only if the object is new)
Student stu1 = new Student();
int count1 = stu1.getNum();
例2：class Student{
static int count;
public static int getNum(){
count++;
return count;
}
}
The main program calls int count2 = Student.getNum();
Second, the static block.
static{
}
Static blocks can only be loaded and run once, first.
例：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, packaging.
1. The function of the package code:
Only provide a name to the outside world, so that the outside world can access these properties or functions.
2. Example: Bank Security
class creditCard{
private double salary; // Salary is not accessible from the outside world, encapsulated
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 is private, only owned by yourself and cannot be accessed by the outside world.