In Java, when to use
Stack<Integer> st = new Stack<Integer>();
and when to use
Stack st = new Stack();
For Stack st = new Stack(), I will have to create my own class Stack, other than this is there any other specific differences between them?
when to use
Stack st = new Stack();?
Never. That style predates the existence of generics in Java. It’s completely replaced by generic usage, i.e. Stack<Integer>. Sometimes you need to use late binding and don’t know which type will be stored inside the stack. But even then you’re supposed to use wildcards, i.e. something like Stack<?>.
A modern IDE will warn you if you use a generic class without specifying generic parameters.
I will have to create my own class
Stack
You don’t, you could use the generic Stack class (that is, java.util.Stack<T>) non-generically. Java allows that (for any generic class, not just for Stack). But it’s discouraged, see above.
