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for java 5.0 and greater.

ArrayList<test> myList = new ArrayList<test>();
test t1 = new test();
myList.add(t1); no error b'se can only put "test" type object
myList.add(new Integer(23));

But if we remove "<test>" from left side

ArrayList myList = new ArrayList<test>(); and now

myList.add(new Integer(23)); no error

But for

ArrayList<test> myList = new ArrayList();

myList.add(new Integer(23)); gives error

Can anyone explain me what i am missing here.

What I have tried:

import java.util.*;

public class Main {

public static void main(String[] args) throws Exception {

ArrayList l = new ArrayList<test>();
l.add(new Integer(3));

}
}

class test{
int i;
void m1(){
System.out.println("inside m1 method");
}

}
Posted
Updated 19-Jan-21 2:53am

1 solution

You are missing many programming concepts, there.
A starting point: Why Use Generics? (The Java™ Tutorials > Learning the Java Language > Generics (Updated))[^]
   
Comments
Mohit Mandloi 19-Jan-21 9:54am
   
understood that ArrayList<test> takes input as "test" type object and return "test" object but i don't understood meaning(or say use) of "<test>" in the following line.

new ArrayList<test>()
CPallini 19-Jan-21 10:00am
   
Creates a collection (an ArrayList) of test objects
Mohit Mandloi 19-Jan-21 10:17am
   
If it's creating arraylist of test objects than why it is allowing different type of object to be assigned in arraylist

ArrayList myList = new ArrayList<test>();

myList.add(new Integer(23)); no error
CPallini 19-Jan-21 10:40am
   
Because you are assigning it to a non-generic ArrayList.
"This is the consequence of a somewhat unfortunate limitation of generic types in Java." From
https://www.informit.com/articles/article.aspx?p=1021579&seqNum=3

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