java嵌套类
A class defined within another class is known as Nested class. The scope of the nested class is bounded by the scope of its enclosing class.
在另一个类中定义的一个类称为嵌套类。 嵌套类的范围受其封闭类的范围限制。
Syntax:
句法：
class Outer{
//class Outer members
class Inner{
//class Inner members
}
} //closing of class Outer
(Advantages of Nested Class)
- It is a way of logically grouping classes that are only used in one place. 这是一种对仅在一个地方使用的类进行逻辑分组的方法。
- It increases encapsulation. 它增加了封装。
- It can lead to more readable and maintainable code. 它可以导致更易读和可维护的代码。
If you want to create a class which is to be used only by the enclosing class, then it is not necessary to create a separate file for that. Instead, you can add it as "Inner Class"
“内部类”
(Static Nested Class)
If the nested class i.e the class defined within another class, has static modifier applied in it, then it is called as static nested class. Since it is, static nested classes can access only static members of its outer class i.e it cannot refer to non-static members of its enclosing class directly. Because of this restriction, static nested class is rarely used.
静态嵌套类
(Non-static Nested class)
Non-static Nested class is the most important type of nested class. It is also known as Inner class. It has access to all variables and methods of Outer class including its private data members and methods and may refer to them directly. But the reverse is not true, that is, Outer class cannot directly access members of Inner class. Inner class can be declared private, public, protected, or with default access whereas an Outer class can have only public or default access.
内部类
One more important thing to notice about an Inner class is that it can be created only within the scope of Outer class. Java compiler generates an error if any code outside Outer class attempts to instantiate Inner class directly.
关于内部类，要注意的另一件事是，只能在外部类的范围内创建它。 如果Outer类之外的任何代码尝试直接实例化Inner类，则Java编译器将生成错误。
A non-static Nested class that is created outside a method is called Member inner class.
成员内部类
A non-static Nested class that is created inside a method is called local inner class. If you want to invoke the methods of local inner class, you must instantiate this class inside the method. We cannot use private, public or protected access modifiers with local inner class. Only abstract and final modifiers are allowed.
local internal class
(Example of Inner class(Member class))
class Outer
{
public void display()
{
Inner in=new Inner();
in.show();
}
class Inner
{
public void show()
{
System.out.println("Inside inner");
}
}
}
class Test
{
public static void main(String[] args)
{
Outer ot = new Outer();
ot.display();
}
}Inside inner
内部内部
(Example of Inner class inside a method(local inner class))
class Outer
{
int count;
public void display()
{
for(int i=0;i<5;i++)
{
//Inner class defined inside for loop
class inner
{
public void show()
{
System.out.println("Inside inner "+(count++));
}
}
Inner in=new Inner();
in.show();
}
}
}
class Test
{
public static void main(String[] args)
{
Outer ot = new Outer();
ot.display();
}
}Inside inner 0 Inside inner 1 Inside inner 2 Inside inner 3 Inside inner 4
内部内部0内部内部1内部内部2内部内部3内部内部4
(Example of Inner class instantiated outside Outer class)
class Outer
{
int count;
public void display()
{
Inner in = new Inner();
in.show();
}
class Inner
{
public void show()
{
System.out.println("Inside inner "+(++count));
}
}
}
class Test
{
public static void main(String[] args)
{
Outer ot = new Outer();
Outer.Inner in = ot.new Inner();
in.show();
}
}Inside inner 1
内里1
(Annonymous class)
Annonymous class.
类称为匿名类
interface Animal
{
void type();
}
public class ATest {
public static void main(String args[])
{
//Annonymous class created
Animal an = new Animal() {
public void type()
{
System.out.println("Annonymous animal");
}
};
an.type();
}
}Annonymous animal
匿名动物
Animal interace and its name will be decided by the compiler. This annonymous class will provide implementation of type()
Animal interace的类，其名称将由编译器决定。 这个匿名类将提供type()方法的实现。
翻译自: https://www.studytonight.com/java/nested-classes.php
java嵌套类
