Below is the code for a Stack program. My question specifically is about the push method, where at the beginning, it checks if (pContent != null). Why does it do that? I commented the if statement out and it still worked fine, so whats the reason for the usage of it. Also , what is the difference between pContent and ContentType here?
Im trying to understand this code I got, Im very thankful for any help.
import greenfoot.*; // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
public class Stacko<ContentType> extends Actor {
/* --------- Anfang der privaten inneren Klasse -------------- */
private class StackNode {
private ContentType content = null;
private StackNode nextNode = null;
public StackNode(ContentType pContent) {
content = pContent;
nextNode = null;
}
public void setNext(StackNode pNext) {
nextNode = pNext;
}
public StackNode getNext() {
return nextNode;
}
public ContentType getContent() {
return content;
}
}
/* ----------- Ende der privaten inneren Klasse -------------- */
private StackNode head;
public void Stack() {
head = null;
}
public boolean isEmpty() {
return (head == null);
}
public void push(ContentType pContent) {
if (pContent != null) {
StackNode node = new StackNode(pContent);
node.setNext(head);
head = node;
}
}
public void pop() {
if (!isEmpty()) {
head = head.getNext();
}
}
public ContentType top() {
if (!this.isEmpty()) {
return head.getContent();
} else {
return null;
}
}
}
