Significance of writting "arraylist<classname>()" while making arraylist object.

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Java

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");
}

}