Introduction to the author
Author name: Ming Shiyin in programming world
Introduction: CSDN blog expert has been engaged in software development for many years and is proficient in Java and JavaScript. Bloggers also learn and grow step by step from scratch, know the importance of learning and accumulation, and like to fight and upgrade with ADC. Welcome to pay attention and look forward to learning, growing and taking off with you!
introduction
Many Java beginners ask me that it's worrying for the novice to turn around and forget the Java knowledge he has studied very hard. How can Xiaobai grow up quickly and become a big cow?
In fact, there is only one skill to become a big God: "learn more and practice more", so brother Ming sorted out typical practice examples. Through practice, you can quickly improve coding skills and proficiency, so that you can never return on the way to become a big man (remember to practice with your own hands)!
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summary
In Java, a class can be defined in another class or a method. Such a class is called an inner class. In a broad sense, internal classes generally include these four types: member internal classes, local internal classes, anonymous internal classes and static internal classes.
The shape is as follows:
If class B is defined in class A, class B is an inner class, also known as a nested class. Relatively speaking, class A is an outer class. If there is multi-layer nesting, for example, there is an inner class B in class A and an inner class C in class B, the outermost class is usually called the top-level class (or top-level class).
Member inner class
Its most common inner class, which is defined as being inside another class.
Example 1
An ordinary inner class
package demo.demo92;
//External class
public class Outer {
class Inner {
// Inner class
}
}
The compiled class file, as shown in the figure:
Conclusion:
The inner class is still an independent class. After compilation, the inner class will be compiled into an independent. Class file, but preceded by the class name and $symbol of the outer class
Example 2
The inner member class can unconditionally access all member properties and member methods of the outer class.
package demo.demo92;
//External class
public class Outer {
private int a=10;
private static int b=20;
private void print(){
System.out.println("External class printing method");
}
private static void static_print(){
System.out.println("External class static Printing method");
}
class Inner {
// Inner class
private void test(){
System.out.println(a);//private attribute of external class
System.out.println(b);//Static properties of external classes
print();//Methods of external classes
static_print();//Static methods of external classes
}
}
}
Example 3
When the inner class of a member has a member variable or method with the same name as the outer class, hiding occurs, that is, by default, the members of the inner class of the member are accessed.
Access to external classes in the following format:
External class. this. Member variable
External class. this. Member method
package demo.demo92;
//External class
public class Outer {
private int a=10;
private void print(){
System.out.println("External class printing method");
}
class Inner {
// Inner class
private int a=10;
private void print(){
System.out.println("External class printing method");
}
private void test(){
System.out.println(a);//private attribute of inner class
print();//Methods of inner classes
System.out.println(Outer.this.a);//private attribute of external class
Outer.this.print();//Methods of external classes
}
}
}
Example 4
Although the member inner class can unconditionally access the members of the external class, if you want to access the members of the member inner class in the external class, you must first create an object of the member inner class, and then access it through a reference to this object.
package demo.demo92;
//External class
public class Outer {
private int a=10;
private void print(){
//Instantiate inner class
Inner inner = new Inner();
//Access through instantiated objects
System.out.println(inner.b);
inner.test();
}
class Inner {
// Inner class
private int b=20;
private void test(){
System.out.println("Inner class test method");
}
}
}
Example 5
If you want to create an object of a member's inner class, you must have an object of an outer class.
package demo.demo92;
//External class
public class Outer {
class Inner {
// Inner class
private int b=20;
public void test(){
System.out.println("Inner class test method");
}
}
}
package demo.demo92;
public class Test {
public static void main(String[] args) {
//Instantiated outer class
Outer outer = new Outer();
//Create an internal class instance from an instance of an external class
Outer.Inner inner = outer.new Inner();
//An instance of the inner class calls the test method
inner.test();
}
}
function:
Internal class test method
Summary
This section summarizes the "Java internal class - member internal class". I hope it can be helpful to you. Please help [like] + [collection] + [punch in the comment area]. If you are interested in learning java with brother Xiaoming, [pay attention to a wave] won't get lost.
Let me know you by punching in the comment area. Mingge will continue to pay attention to your learning progress!
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