From 97719c607604371c67acde47e963f8eeeb9bac52 Mon Sep 17 00:00:00 2001
From: Vansh Dhar <vanshdhar@iisc.ac.in>
Date: Fri, 4 Oct 2024 20:11:57 +0530
Subject: [PATCH] edit java/SinglyLinkedList.java

---
 README.md                      |   4 +-
 src/java/SinglyLinkedList.java | 159 +++++++++++++++++++++++++++++++++
 2 files changed, 161 insertions(+), 2 deletions(-)
 create mode 100644 src/java/SinglyLinkedList.java

diff --git a/README.md b/README.md
index bcde5a3d..f388d228 100644
--- a/README.md
+++ b/README.md
@@ -2109,8 +2109,8 @@ In order to achieve greater coverage and encourage more people to contribute to
                 </a>
             </td>
             <td> <!-- Java -->
-                <a href="./CONTRIBUTING.md">
-                    <img align="center" height="25" src="./logos/github.svg" />
+                <a href="./src/java/SinglyLinkedList.java">
+                    <img align="center" height="25" src="./logos/java.svg" />
                 </a>
             </td>
             <td> <!-- Python -->
diff --git a/src/java/SinglyLinkedList.java b/src/java/SinglyLinkedList.java
new file mode 100644
index 00000000..90b9de2b
--- /dev/null
+++ b/src/java/SinglyLinkedList.java
@@ -0,0 +1,159 @@
+import java.util.Objects;
+
+class Node {
+    int val;
+    Node next;
+
+    Node(int val) {
+        this.val = val;
+        this.next = null;
+    }
+
+    Node(int val, Node next) {
+        this.val = val;
+        this.next = next;
+    }
+}
+
+public class SinglyLinkedList {
+    Node head;
+
+    public void printList() {
+        Node aux = head;
+        System.out.print("[");
+        while (aux != null) {
+            System.out.print(aux.val);
+            if (aux.next != null) {
+                System.out.print(", ");
+            }
+            aux = aux.next;
+        }
+        System.out.println("]");
+    }
+
+    public void pushBack(int val) {
+        Node newNode = new Node(val);
+        if (head == null) {
+            head = newNode;
+        } else {
+            Node aux = head;
+            while (aux.next != null) {
+                aux = aux.next;
+            }
+            aux.next = newNode;
+        }
+    }
+
+    public void pushFront(int val) {
+        Node newNode = new Node(val, head);
+        head = newNode;
+    }
+
+    public void insertInPosition(int val, int pos) {
+        if (pos == 0) {
+            pushFront(val);
+            return;
+        }
+        Node newNode = new Node(val);
+        Node prev = head;
+        Node curr = head;
+
+        while (curr != null && pos > 0) {
+            prev = curr;
+            curr = curr.next;
+            pos--;
+        }
+
+        prev.next = newNode;
+        newNode.next = curr;
+    }
+
+    public void popBack() {
+        if (head == null) {
+            return;
+        }
+
+        if (head.next == null) {
+            head = null;
+            return;
+        }
+
+        Node prev = head;
+        Node curr = head.next;
+
+        while (curr.next != null) {
+            prev = prev.next;
+            curr = curr.next;
+        }
+
+        prev.next = null;
+    }
+
+    public void popFront() {
+        if (head == null) {
+            return;
+        }
+
+        Node aux = head;
+        head = aux.next;
+    }
+
+    public void removeFromPosition(int pos) {
+        if (head == null) {
+            return;
+        }
+
+        if (pos == 0) {
+            popFront();
+            return;
+        }
+
+        Node prev = head;
+        Node curr = head;
+
+        while (curr != null && pos > 0) {
+            prev = curr;
+            curr = curr.next;
+            pos--;
+        }
+
+        if (curr != null) {
+            prev.next = curr.next;
+        }
+    }
+
+    public static void main(String[] args) {
+        SinglyLinkedList list = new SinglyLinkedList();
+
+        System.out.println("Inserting the elements at the end [1, 2, 3]:");
+        list.pushBack(1);
+        list.pushBack(2);
+        list.pushBack(3);
+        list.printList();
+
+        System.out.println("Inserting the elements at the beginning [0, -1, -2]:");
+        list.pushFront(0);
+        list.pushFront(-1);
+        list.pushFront(-2);
+        list.printList();
+
+        System.out.println("Inserting in positions 3, 4, 5 the elements [997, 998, 999] respectively:");
+        list.insertInPosition(997, 3);
+        list.insertInPosition(998, 4);
+        list.insertInPosition(999, 5);
+        list.printList();
+
+        System.out.println("Removing last element:");
+        list.popBack();
+        list.printList();
+
+        System.out.println("Removing first element:");
+        list.popFront();
+        list.printList();
+
+        System.out.println("Removing element in position 2:");
+        list.removeFromPosition(2);
+        list.printList();
+    }
+}
+