java simple perception in four access modifiers

The four access modifiers are (private by default protected public) access to this sort by the size of the (small to large)

Test 1: This category is performed

package Demo1;

public class Test {
    private void show1(){
        System.out.println("show1 private");
    }

    void show2(){
        System.out.println("show2 默认");
    }

    protected void show3(){
        System.out.println("show3 protected");
    }
    public void show4(){
        System.out.println("show4 public");
    }

    public static void main(String[] args) {
        Test test = new Test();
        test.show1();
        test.show2();
        test.show3();
        test.show4();
    }
}
输出结果

show1 private
show2 默认
show3 protected
show4 public

The results showed that: In this class, the four modifier modified methods are accessible.

Test 2: the same package class

package Demo1;

class Test2 {public 
    public static void main (String [] args) { 
        the Test Test new new = the Test (); 
        test.show1 (); 
        test.show2 (); 
        test.show3 (); 
        test.show4 (); 
    } 
} 
error : java: show1 () is the private access control Demo1.Test 
the test.show1 (); commented

package Demo1;

public class Test2 {
    public static void main(String[] args) {
        Test test = new Test();
//        test.show1();
        test.show2();
        test.show3();
        test.show4();
    }
}
结果

show2 default
show3 protected
show4 public

In the sub-category

package Demo1;

Son the extends the Test class {public 
    public static void main (String [] args) { 
        the Test Test new new = the Test (); 
// test.show1 (); 
        test.show2 (); 
        test.show3 (); 
        test.show4 () ; 
    } 
} 
with the same results of the implementation test1 

results show that: under the same package type, except for private use can not be called a modified rest could be called. 

Test 3: class in different packages

Demo2 Package; 

Import Demo1.Test; 

public class Son the extends the Test { 
    public static void main (String [] args) { 
        the Test Test new new = the Test (); // other classes in different packages 
// test.show1 (); 
/ / test.show2 (); 
// test.show3 (); 
        test.show4 (); 
        System.out.println ( "-----------"); 
        Son Son = Son new new (); // subclasses in different packages   
// son.show1 (); 
// son.show2 (); 
        son.show3 (); 
        son.show4 (); 
    } 
} 
results

show4 public
-----------
show3 protected
show4 public

The results show that: under different subclasses package may call (protected, public), can only call other classes (public) in different packages

to sum up:

1. Private : emphasize their use in this class;

2. Default : emphasize the use of the package in the same class;

3. protected : emphasize the use by subclasses;

4. public: stressed that everyone can use;