Double Linked List Faldi

Class Node :

int data;
Node next;
Node prev;

public Node(int data) {
    this.data = data;
}

public void tampil() {
    System.out.print("{"+data+"}");
}

Class DoubleLinkedList :

Node awal;
Node akhir;

public DoubleLinkedList() {
    awal = null;
    akhir = null;
}

public boolean isEmpty() {
    return (awal==null);
}

public void insertAwal(int data) {
    Node node = new Node(data);
    if(isEmpty()) {
        akhir = node;
    } else {
        awal.prev = node;
    }

    node.next = awal;
    awal = node;
}

public void insertAkhir(int data) {
    Node node = new Node(data);
    if(isEmpty()) {
        awal = node;
    } else {
        akhir.next = node;
        node.prev = akhir;
    }
    akhir = node;
}

public Node deleteAwal() {
    Node temp = awal;
    if(awal.next == null) {
        akhir = null;
    } else {
        awal.next.prev = null;
    }
    awal = awal.next;
    return temp;
}

public Node deleteAkhir() {
    Node temp = akhir;
    if(awal.next == null) {
        awal = null;
    } else {
        akhir.prev.next = null;
    }
    akhir = akhir.prev;
    return temp;
}

public boolean insertAfter(int key, int data) {
    Node current = awal;
    while(current.data != key) {
        current = current.next;
        if(current == null)
        return false;
    }
    Node node = new Node(data);

    if(current == akhir) {
        node.next = null;
        akhir = node;
    } else {
        node.next = current.next;
        current.next.prev = node;
    }
    node.prev = current;
    current.next = node;
    return true;
}

public Node deleteKey(int key) {
    Node current = awal;
    while(current.data != key) {
        current = current.next;
    }
    if(current == null) {
        return null;
    }
    if(current == awal)
        awal = current.next;
    else
        current.prev.next = current.next;
    if(current == akhir)
        akhir = current.prev
    else
        current.next.prev = current.prev;
        return current;
}

public void displayForward() {
    System.out.print("List (awal-->akhir): ");
    Node current = awal;

    while(current != null) {
        current.tampil();
        current = current.next;
    }
    System.out.println("");
}

public void displayForward() {
    System.out.print("List (akhir-->awal): ");
    Node current = akhir;

    while(current != null) {
        current.tampil();
        current = current.prev;
    }
    System.out.println("");
}