Latihan Queue

 Source code class main:

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        cQueue antrian = new cQueue();
        Scanner s = new Scanner(System.in);
        int pilih = 0;
        do {
            System.out.println("======================================");
            System.out.println("            Aplikasi Queue            ");
            System.out.println("======================================");
            System.out.println("                                      ");
            System.out.println("1. Tambah Barang                      ");
            System.out.println("2. List Daftar Antrian Semua Barang   ");
            System.out.println("3. Lihat Proses Barang                ");
            System.out.println("4. Exit");
            System.out.println("                                      ");
            System.out.print("Pilih : ");
            pilih = s.nextInt();
            System.out.println("");
            switch(pilih) {
                case 1:
                    System.out.println("======================================");
                    System.out.print("Masukkan nama barang  : ");
                    String namaBarang = s.next();
                    System.out.print("Masukkan harga barang : ");
                    int hargaBarang = s.nextInt();
                    cDaftarJualan barangBaru = new cDaftarJualan(namaBarang, hargaBarang);
                    antrian.enqueue(barangBaru);
                    System.out.println("Barang Masuk List..");
                    System.out.println("======================================");
                    System.out.println("");
                    break;
                case 2:
                    System.out.println("======================================");
                    System.out.println("List Antrian Pembelian Barang :");
                    System.out.println("                               ");
                    if (antrian.isEmpty()) {
                        System.out.println("Tidak Ada Antrian Barang..");
                        System.out.println("                                      ");
                    } else {
                        cNode current = antrian.front;
                        int nomorUrut = 1;
                        while (current != null) {
                            cDaftarJualan barang = current.getData();
                            System.out.println(nomorUrut + ". Nama  : " + barang.getNama());
                            System.out.println("   Harga : " + "Rp." + barang.getHarga());
                            current = current.getNext();
                            nomorUrut++;
                            System.out.println("                                      ");
                        }
                        System.out.println("======================================");
                        System.out.println("                                      ");
                    }
                    break;
                case 3:
                    if (antrian.isEmpty()) {
                        System.out.println("======================================");
                        System.out.println("Daftar Proses Barang : ");
                        System.out.println("Antrian kosong...");
                        System.out.println("======================================");
                        System.out.println("                                      ");
                    } else {
                        cDaftarJualan barangDiproses = antrian.dequeue();
                        System.out.println("======================================");
                        System.out.println("Lihat Proses Barang : ");
                        System.out.println("                      ");
                        System.out.println("Nama  : " + barangDiproses.getNama());
                        System.out.println("Harga : Rp.1" + barangDiproses.getHarga());
                        System.out.println("======================================");
                        System.out.println("                                      ");
                    }
                    break;
                case 4:
                    System.out.println("======================================");
                    System.out.println("              Terima Kasih            ");
                    System.out.println("======================================");
                    break;
            }
            System.out.println();
        } while(pilih != 4);
    }
}

Source code class cNode:

public class cNode  {
    private cDaftarJualan data;
    private cNode next;
    public cNode(cDaftarJualan d) {
        data = d;
    }
    public cDaftarJualan getData() {
        return data;
    }
    public cNode getNext() {
        return next;
    }
    public void setNext(cNode n) {
        next = n;
    }
}

Source code class cDaftarJualan:

public class cDaftarJualan {
    private String nama;
    private int harga;
    public cDaftarJualan(String n, int h) {
        nama = n;
        harga = h;
    }
    public String getNama() {
        return nama;
    }
    public int getHarga() {
        return harga;
    }
}

Source code class cQueue:

public class cQueue {
    cNode front;
    cNode rear;
    public boolean isEmpty() {
        return front == null;
    }
    public void enqueue(cDaftarJualan data) {
        cNode newNode = new cNode(data);
        if (isEmpty()) {
            front = newNode;
            rear = newNode;
        } else {
            rear.setNext(newNode);
            rear = newNode;
        }
    }
    public cDaftarJualan dequeue() {
        if (isEmpty()) {
            throw new IllegalStateException("Antrian kosong...");
        }
        cDaftarJualan data = front.getData();
        front = front.getNext();
        if(front == null) {
            rear = null;
        }
        return data;
    }
    public cDaftarJualan peek() {
        if (isEmpty()) {
            throw new IllegalStateException("Antrian kosong...");
        }
        return front.getData();
    }

}

Output Run Programs: