Java generic usage, Java generic usage

Java generic usage, Java generic usage
In Java, generics use generics:

Generic: you do not need to convert the collection class to add objects.

Reflection mechanism: display all methods and members of generic fixed classes

 

Core code:

ArrayList <Ls> ff = new ArrayList () <Ls>;

Ls ls1 = new Ls ("Potato Chips", 5f );

Ff. add (ls1 );

Ls cls = ff. get (0); // strong conversion is not required here

 

 

Code example:

Note: This is non-Generic Code, which requires strong conversion when calling objects in the Collection class.

Import java. util .*;

Public class L4_6

{

Public static void main (String [] args)

{

// Hashtable ff = new Hashtable ();

ArrayList ff = new ArrayList ();

Ls ls1 = new Ls ("Potato Chips", 5f );

Ff. add (ls1 );

Ls cls = (Ls) ff. get (0 );

Yl hyl = (Yl) ff. get (0); // This is obviously incorrect.

}

}

Class Ls

{

Private String mingcheng;

Private float jiage;

Ls (String mingcheng, float jiage)

{

This. mingcheng = mingcheng;

This. jiage = jiage;

}

}

Class Yl

{

Private String mingcheng;

Private float jiage;

Private String yanse;

Yl (String mingcheng, float jiage, String yanse)

{

This. mingcheng = mingcheng;

This. jiage = jiage;

This. yanse = yanse;

}

}