Summary of Java Generics Example Tutorial
Generics are a very important knowledge point in Java. Generics are widely used in the Java collection class framework. In this article, we will look at the Java generic
Automobile class from scratch:
public class Automobile { private String name; public Automobile(String name){ this.name= name;
} public String getName() { return name;
} public void setName(String name) { this.name = name;
}
}Holder1 class: holds a specified single type object.
public class Holder1 { private Automobile automobile; public Holder1(Automobile automobile){ this.automobile = automobile;
} public Automobile get(){ return this.automobile;
}
}Holder2 class: holds Object object.
public class Holder2 { private Object object; public Holder2(Object object){ this.setObject(object);
} public Object getObject() { return object;
} public void setObject(Object object) { this.object = object;
}
}Holder3 class: Use generics to hold a single object, but do not specify its type for the time being, and decide what kind of object to hold when using it.
public class Holder3 <T>{ private T t; public Holder3(T t){ this.setT(t);
} public T getT() { return t;
} public void setT(T t) { this.t = t;
}
}Main program Main:
public class Main { public static void main(String[] args) { /*使用Holder1*/
Holder1 holder1 = new Holder1(new Automobile("Iphone"));
System.out.println(holder1.get().getName());
/*使用Holder2*/
//使holder2持有String类型对象
Holder2 holder2 = new Holder2("XiaoMi");
System.out.println(holder2.getObject());
//更改holder2中持有的对象类型
holder2.setObject(new Automobile("HuaWei")); //向下转型Object->Automobile
Automobile automobile = (Automobile) holder2.getObject();
System.out.println(automobile.getName());
/*使用Holder3*/
//告诉编译器holder3持有的对象类型为String //此时holder3拥有的对象类型只能为String，不能变更
Holder3<String> holder3 = new Holder3<String>("Vivo");
System.out.println(holder3.getT()); //告诉编译器anotherHolder3持有的对象类型为Automobile //此时anotherHolder3拥有的对象类型只能为Automobile，不能变更
Holder3<Automobile> anotherHolder3 = new Holder3<Automobile>(new Automobile("Oneplus"));
System.out.println(anotherHolder3.getT().getName());
}
}The program running result is:
Iphone XiaoMi HuaWei Vivo Oneplus
[Related recommendations]
2. Java Generics Summary (3) - Detailed explanation of the use of wildcards
3. Java Generics Summary (2) - Generics and Array
3. Summary of Java generics (1) - Detailed explanation of basic usage and type erasure
4. Examples of java generics Detailed code explanation
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