Java Collections - PriorityQueue.add() Examples

package com.logicbig.example.priorityqueue;

import java.util.PriorityQueue;

public class AddExample {

    public static void main(String... args) {
        PriorityQueue<String> pq = new PriorityQueue<>();
        pq.add("one");
        pq.add("two");
        System.out.println(pq);
    }
}

Output

[one, two]

PriorityQueue does not allow null elements:

package com.logicbig.example.priorityqueue;

import java.util.PriorityQueue;

public class AddExample2 {

    public static void main(String... args) {
        PriorityQueue<String> pq = new PriorityQueue<>();
        pq.add(null);
    }
}

Output

java.lang.NullPointerException
    at java.util.PriorityQueue.offer (PriorityQueue.java:325)
    at java.util.PriorityQueue.add (PriorityQueue.java:311)
    at com.logicbig.example.priorityqueue.AddExample2.main (AddExample2.java:15)
    at jdk.internal.reflect.DirectMethodHandleAccessor.invoke (DirectMethodHandleAccessor.java:104)
    at java.lang.reflect.Method.invoke (Method.java:565)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.executeMainMethod (AbstractExecJavaBase.java:402)
    at org.codehaus.mojo.exec.ExecJavaMojo.executeMainMethod (ExecJavaMojo.java:142)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.doExecClassLoader (AbstractExecJavaBase.java:377)
    at org.codehaus.mojo.exec.AbstractExecJavaBase.lambda$execute$0 (AbstractExecJavaBase.java:287)
    at java.lang.Thread.run (Thread.java:1474)