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Add LotteryScheduling algorithm (#5656)
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‎DIRECTORY.md

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* [FCFSScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/FCFSScheduling.java)
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* [HighestResponseRatioNextScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/HighestResponseRatioNextScheduling.java)
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* [JobSchedulingWithDeadline](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/JobSchedulingWithDeadline.java)
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* [LotteryScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/LotteryScheduling.java)
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* [MLFQScheduler](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/MLFQScheduler.java)
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* [NonPreemptivePriorityScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/NonPreemptivePriorityScheduling.java)
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* [PreemptivePriorityScheduling](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/scheduling/PreemptivePriorityScheduling.java)
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* [FCFSSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/FCFSSchedulingTest.java)
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* [HighestResponseRatioNextSchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/HighestResponseRatioNextSchedulingTest.java)
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* [JobSchedulingWithDeadlineTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/JobSchedulingWithDeadlineTest.java)
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* [LotterySchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/LotterySchedulingTest.java)
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* [MLFQSchedulerTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/MLFQSchedulerTest.java)
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* [NonPreemptivePrioritySchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/NonPreemptivePrioritySchedulingTest.java)
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* [PreemptivePrioritySchedulingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/scheduling/PreemptivePrioritySchedulingTest.java)

‎pom.xml

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<version>${assertj.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-core</artifactId>
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<version>5.14.1</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.junit.jupiter</groupId>

‎src/main/java/com/thealgorithms/scheduling/LotteryScheduling.java

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package com.thealgorithms.scheduling;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Random;
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/**
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* The LotteryScheduling class implements the Lottery Scheduling algorithm, which is
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* a probabilistic CPU scheduling algorithm. Processes are assigned tickets, and
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* the CPU is allocated to a randomly selected process based on ticket count.
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* Processes with more tickets have a higher chance of being selected.
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*/
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public final class LotteryScheduling {
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private LotteryScheduling() {
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}
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private List<Process> processes;
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private Random random;
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/**
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* Constructs a LotteryScheduling object with the provided list of processes.
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*
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* @param processes List of processes to be scheduled using Lottery Scheduling.
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*/
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public LotteryScheduling(final List<Process> processes) {
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this.processes = processes;
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this.random = new Random();
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}
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/**
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* Constructs a LotteryScheduling object with the provided list of processes and a Random object.
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*
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* @param processes List of processes to be scheduled using Lottery Scheduling.
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* @param random Random object used for generating random numbers.
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*/
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public LotteryScheduling(final List<Process> processes, Random random) {
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this.processes = processes;
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this.random = random;
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}
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/**
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* Schedules the processes using the Lottery Scheduling algorithm.
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* Each process is assigned a certain number of tickets, and the algorithm randomly
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* selects a process to execute based on ticket count. The method calculates the
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* waiting time and turnaround time for each process and simulates their execution.
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*/
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public List<Process> scheduleProcesses() {
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int totalTickets = processes.stream().mapToInt(Process::getTickets).sum();
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int currentTime = 0;
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List<Process> executedProcesses = new ArrayList<>();
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while (!processes.isEmpty()) {
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int winningTicket = random.nextInt(totalTickets) + 1;
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Process selectedProcess = selectProcessByTicket(winningTicket);
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if (selectedProcess == null) {
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// This should not happen in normal circumstances, but we'll handle it just in case
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System.err.println("Error: No process selected. Recalculating total tickets.");
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totalTickets = processes.stream().mapToInt(Process::getTickets).sum();
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continue;
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}
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selectedProcess.setWaitingTime(currentTime);
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currentTime += selectedProcess.getBurstTime();
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selectedProcess.setTurnAroundTime(selectedProcess.getWaitingTime() + selectedProcess.getBurstTime());
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executedProcesses.add(selectedProcess);
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processes.remove(selectedProcess);
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totalTickets = processes.stream().mapToInt(Process::getTickets).sum();
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}
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return executedProcesses;
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}
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/**
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* Selects a process based on a winning ticket. The method iterates over the
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* list of processes, and as the ticket sum accumulates, it checks if the
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* current process holds the winning ticket.
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*
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* @param winningTicket The randomly generated ticket number that determines the selected process.
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* @return The process associated with the winning ticket.
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*/
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private Process selectProcessByTicket(int winningTicket) {
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int ticketSum = 0;
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for (Process process : processes) {
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ticketSum += process.getTickets();
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if (ticketSum >= winningTicket) {
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return process;
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}
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}
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return null;
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}
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/**
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* The Process class represents a process in the scheduling system. Each process has
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* an ID, burst time (CPU time required for execution), number of tickets (used in
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* lottery selection), waiting time, and turnaround time.
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*/
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public static class Process {
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private String processId;
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private int burstTime;
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private int tickets;
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private int waitingTime;
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private int turnAroundTime;
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public Process(String processId, int burstTime, int tickets) {
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this.processId = processId;
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this.burstTime = burstTime;
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this.tickets = tickets;
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}
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public String getProcessId() {
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return processId;
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}
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public int getBurstTime() {
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return burstTime;
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}
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public int getTickets() {
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return tickets;
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}
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public int getWaitingTime() {
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return waitingTime;
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}
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public void setWaitingTime(int waitingTime) {
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this.waitingTime = waitingTime;
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}
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public int getTurnAroundTime() {
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return turnAroundTime;
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}
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public void setTurnAroundTime(int turnAroundTime) {
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this.turnAroundTime = turnAroundTime;
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}
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}
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}

‎src/test/java/com/thealgorithms/scheduling/LotterySchedulingTest.java

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package com.thealgorithms.scheduling;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.mockito.Mockito.mock;
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import static org.mockito.Mockito.when;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Random;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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public class LotterySchedulingTest {
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private Random mockRandom;
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@BeforeEach
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public void setup() {
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mockRandom = mock(Random.class);
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}
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@Test
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public void testLotterySchedulingWithMockedRandom() {
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List<LotteryScheduling.Process> processes = createProcesses();
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LotteryScheduling lotteryScheduling = new LotteryScheduling(processes, mockRandom);
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// Mock the sequence of random numbers (winning tickets)
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// This sequence ensures that P1 (10 tickets), P3 (8 tickets), and P2 (5 tickets) are selected.
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when(mockRandom.nextInt(23)).thenReturn(5, 18, 11); // winning tickets for P1, P3, and P2
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List<LotteryScheduling.Process> executedProcesses = lotteryScheduling.scheduleProcesses();
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assertEquals(3, executedProcesses.size());
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// Assert the process execution order and properties
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LotteryScheduling.Process process1 = executedProcesses.get(0);
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assertEquals("P1", process1.getProcessId());
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assertEquals(0, process1.getWaitingTime());
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assertEquals(10, process1.getTurnAroundTime());
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LotteryScheduling.Process process2 = executedProcesses.get(1);
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assertEquals("P2", process2.getProcessId());
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assertEquals(10, process2.getWaitingTime());
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assertEquals(15, process2.getTurnAroundTime());
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LotteryScheduling.Process process3 = executedProcesses.get(2);
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assertEquals("P3", process3.getProcessId());
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assertEquals(15, process3.getWaitingTime());
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assertEquals(23, process3.getTurnAroundTime());
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}
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private List<LotteryScheduling.Process> createProcesses() {
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LotteryScheduling.Process process1 = new LotteryScheduling.Process("P1", 10, 10); // 10 tickets
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LotteryScheduling.Process process2 = new LotteryScheduling.Process("P2", 5, 5); // 5 tickets
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LotteryScheduling.Process process3 = new LotteryScheduling.Process("P3", 8, 8); // 8 tickets
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List<LotteryScheduling.Process> processes = new ArrayList<>();
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processes.add(process1);
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processes.add(process2);
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processes.add(process3);
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return processes;
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}
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}

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