How do I create a Linked List Data Structure in Java?
JavaData StructuresLinked ListJava Problem Overview
What's the best way to make a linked list in Java?
Java Solutions
Solution 1 - Java
The obvious solution to developers familiar to Java is to use the LinkedList class already provided in java.util. Say, however, you wanted to make your own implementation for some reason. Here is a quick example of a linked list that inserts a new link at the beginning of the list, deletes from the beginning of the list and loops through the list to print the links contained in it. Enhancements to this implementation include making it a double-linked list, adding methods to insert and delete from the middle or end, and by adding get and sort methods as well.
Note: In the example, the Link object doesn't actually contain another Link object - nextLink is actually only a reference to another link.
class Link {
public int data1;
public double data2;
public Link nextLink;
//Link constructor
public Link(int d1, double d2) {
data1 = d1;
data2 = d2;
}
//Print Link data
public void printLink() {
System.out.print("{" + data1 + ", " + data2 + "} ");
}
}
class LinkList {
private Link first;
//LinkList constructor
public LinkList() {
first = null;
}
//Returns true if list is empty
public boolean isEmpty() {
return first == null;
}
//Inserts a new Link at the first of the list
public void insert(int d1, double d2) {
Link link = new Link(d1, d2);
link.nextLink = first;
first = link;
}
//Deletes the link at the first of the list
public Link delete() {
Link temp = first;
if(first == null){
return null;
//throw new NoSuchElementException(); // this is the better way.
}
first = first.nextLink;
return temp;
}
//Prints list data
public void printList() {
Link currentLink = first;
System.out.print("List: ");
while(currentLink != null) {
currentLink.printLink();
currentLink = currentLink.nextLink;
}
System.out.println("");
}
}
class LinkListTest {
public static void main(String[] args) {
LinkList list = new LinkList();
list.insert(1, 1.01);
list.insert(2, 2.02);
list.insert(3, 3.03);
list.insert(4, 4.04);
list.insert(5, 5.05);
list.printList();
while(!list.isEmpty()) {
Link deletedLink = list.delete();
System.out.print("deleted: ");
deletedLink.printLink();
System.out.println("");
}
list.printList();
}
}
Solution 2 - Java
Java has a LinkedList implementation, that you might wanna check out. You can download the JDK and it's sources at java.sun.com.
Solution 3 - Java
Use java.util.LinkedList. Like this:
list = new java.util.LinkedList()
Solution 4 - Java
The above linked list display in opposite direction. I think the correct implementation of insert method should be
public void insert(int d1, double d2) {
Link link = new Link(d1, d2);
if(first==null){
link.nextLink = null;
first = link;
last=link;
}
else{
last.nextLink=link;
link.nextLink=null;
last=link;
}
}
Solution 5 - Java
Its much better to use java.util.LinkedList, because it's probably much more optimized, than the one that you will write.
Solution 6 - Java
//slightly improved code without using collection framework
package com.test;
public class TestClass {
private static Link last;
private static Link first;
public static void main(String[] args) {
//Inserting
for(int i=0;i<5;i++){
Link.insert(i+5);
}
Link.printList();
//Deleting
Link.deletefromFirst();
Link.printList();
}
protected static class Link {
private int data;
private Link nextlink;
public Link(int d1) {
this.data = d1;
}
public static void insert(int d1) {
Link a = new Link(d1);
a.nextlink = null;
if (first != null) {
last.nextlink = a;
last = a;
} else {
first = a;
last = a;
}
System.out.println("Inserted -:"+d1);
}
public static void deletefromFirst() {
if(null!=first)
{
System.out.println("Deleting -:"+first.data);
first = first.nextlink;
}
else{
System.out.println("No elements in Linked List");
}
}
public static void printList() {
System.out.println("Elements in the list are");
System.out.println("-------------------------");
Link temp = first;
while (temp != null) {
System.out.println(temp.data);
temp = temp.nextlink;
}
}
}
}