Difference between add() and offer() in Queue

[Satyajeet Kadam]

Q1) What is difference between add() and offer() in priorityQueue

As per both methods throw an ClassCastException if element that is to be added cannot be compared with elements already present in the Queue.

NullPointerException if the specified element is null.

I found the add() internally calls the offer()

    public boolean add(E e) {
        return offer(e);
    }

public boolean offer(E e) {
        if (e == null)
            throw new NullPointerException();
        modCount++;
        int i = size;
        if (i >= queue.length)
            grow(i + 1);
        size = i + 1;
        if (i == 0)
            queue[0] = e;
        else
            siftUp(i, e);
        return true;
    }

Q2)why there are two methods for same operations

[Seetharaman Venkatasamy]

they are same. but the methods are used in different context.
Queue is a Collection. and offer() is in Queue. consider below code,

Collection c = new PriorityQueue();
//how do you access offer method of PriorityQueue here?

[Satyajeet Kadam]

Can you please elaborate your answer?

[Eduardo Mineo]

Satyajeet, you can see in SunOracle Queue specification:

The offer method inserts an element if possible, otherwise returning false. This differs from the Collection.add method, which can fail to add an element only by throwing an unchecked exception. The offer method is designed for use when failure is a normal, rather than exceptional occurrence, for example, in fixed-capacity (or "bounded") queues.

--eduardo