PriorityBlockingQueue add() Method in Java

The add(E e) method of PriorityBlockingQueue inserts the element passed as a parameter to the method at the tail of this PriorityBlockingQueue. This method returns true if the adding of the element is successful. Else it returns false. 

Syntax:

public boolean add(E e)

Parameter: This method takes a mandatory parameter e which is the element to be inserted in PriorityBlockingQueue. 

Returns: This method returns a boolean response. It returns true if the adding of the element is successful, else it returns false. 

Exception: This method throws following exceptions:

• ClassCastException: if the element passed as parameter cannot be compared to the element contained by queue to keep priority queue's ordering.
• NullPointerException: if the element passed as parameter is null.

Below program illustrate  add() method of PriorityBlockingQueue: 

Example 1: 

After Adding Some Numbers
PriorityBlockingQueue:[526734, 84879456, 4586415]

After adding Some More Numbers
PriorityBlockingQueue:[156116, 526734, 4586415, 84879456, 61651191]

Example 2: To demonstrate NullPointerException thrown by add() method. 

Exception when adding null: java.lang.NullPointerException

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/PriorityBlockingQueue.html#add-E-