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This article introduces the relevant knowledge of "what is the method of Java defining generic interfaces and classes". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

A little bit of eye contact

The so-called generics: allows you to specify type parameters when defining classes and interfaces, which will be determined when you declare variables and create objects (that is, passing in the actual type parameters, also known as type arguments).

JDK1.5 rewrites all interfaces and classes in the collection framework, adding generic support to these interfaces and classes, so that type arguments can be passed in when declaring collection variables and creating collection objects.

Second actual combat

1 code

/ / the generic declaration public class Apple {/ / uses the T-type formal parameter to define the instance variable private T info; public Apple () {} / / the T-type formal parameter is used to define the constructor public Apple (T info) {this.info = info;} public void setInfo (T info) {this.info = info;} public T getInfo () {return this.info } public static void main (String [] args) {/ / because the constructor parameter is passed to the T-parameter String, so the constructor parameter can only be String Apple A1 = new Apple ("apple"); System.out.println (a1.getInfo ()); / / because it is passed to the T-parameter Double, so the constructor parameter can only be Double or double Apple a2 = new Apple; System.out.println (a2.getInfo ());}}

2 run

Apple 5.67

3 description

When you create a generic class, when you define a constructor for that class, the constructor name is the same as the original class name, and do not add the generic declaration. For example, when you define a constructor for an Apple class, the constructor is still Apple, not Apple.

When you call the constructor, you can use the form of Apple, and of course you should pass in the actual type parameters for the T-parameter. Java 7 provides diamond syntax that allows you to omit type arguments in.

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