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SJF.java
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SJF.java
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import java.util.ArrayList;
public class SJF {
private ArrayList<Process> SJFqueue = new ArrayList<Process>();
private ArrayList<Process> activeProcesses = new ArrayList<Process>();
private ArrayList<Process> inactiveProcesses;
private Process currentlyWorkingProcess;
private Process previousWorkingProcess;
private int clock = 0;
private boolean switchOccurred = false;
private int switchTime = 0;
public SJF(ArrayList<Process> processes, int contextSwitchTime) {
inactiveProcesses = new ArrayList<>(processes);
switchTime = contextSwitchTime;
while(activeProcesses.size()!=0 || clock==0){
moveInactiveToActive();
calculateRemainingTime();
chooseCurrentlyWorkingProcess();
if(switchOccurred && switchTime!=0)
clock+=contextSwitchTime;
else {
SJFqueue.add(currentlyWorkingProcess);
//System.out.println("current working process " + currentlyWorkingProcess.getProcessName() + " At clock = " + clock);
clock+=1;
}
}
printOrder();
calculateTime(processes);
}
private void moveInactiveToActive(){
for (int i = 0; i < inactiveProcesses.size(); i++) {
Process tempProcess = inactiveProcesses.get(i);
if(tempProcess.getArrivalTime() <= clock){
activeProcesses.add(tempProcess);
inactiveProcesses.remove(tempProcess);
}
}
}
private void calculateRemainingTime(){
if (clock != 0){
int currentRemainingTime = currentlyWorkingProcess.getRemainingTime();
if(!switchOccurred || switchTime==0){
currentRemainingTime -=1;
currentlyWorkingProcess.setRemainingTime(currentRemainingTime);
if(currentRemainingTime==0){
currentlyWorkingProcess.setEndTime(clock);
activeProcesses.remove(currentlyWorkingProcess);
}
}
}
}
private void chooseCurrentlyWorkingProcess() {
if (activeProcesses.size() != 0) {
int index = 0;
int min = activeProcesses.get(index).getRemainingTime();
switchOccurred = false;
if (clock != 0)
previousWorkingProcess = currentlyWorkingProcess;
for (int i = 0; i < activeProcesses.size(); i++) {
if (activeProcesses.get(i).getRemainingTime() < min && activeProcesses.get(i).getRemainingTime() !=0) {
index = i;
min = activeProcesses.get(index).getRemainingTime();
}
}
currentlyWorkingProcess = activeProcesses.get(index);
if (clock != 0 && !currentlyWorkingProcess.equals(previousWorkingProcess))
switchOccurred = true;
}
}
private void calculateTime(ArrayList<Process> processes){
int waitSum = 0;
int waitTime;
int turnAroundSum = 0;
int turnAround;
for (int i = 0; i < processes.size(); i++) {
waitTime = processes.get(i).getEndTime() - processes.get(i).getArrivalTime() - processes.get(i).getBurstTime();
turnAround = processes.get(i).getEndTime() - processes.get(i).getArrivalTime();
System.out.println("waiting time for process " + processes.get(i).getProcessName() + " is " + waitTime);
System.out.println("turnAround time for process " + processes.get(i).getProcessName() + " is " +turnAround);
waitSum+= waitTime;
turnAroundSum+=turnAround;
}
float avgWaitTime = (float)waitSum/(float)processes.size();
float avgTurnAroundTime = (float)turnAroundSum/(float)processes.size();
System.out.println("average waiting time for SJF: " + avgWaitTime);
System.out.println("average turnAround time for SJF: " + avgTurnAroundTime);
}
private void printOrder(){
for (int i = 0; i < SJFqueue.size()-1; i++) {
System.out.print(SJFqueue.get(i).getProcessName());
}
System.out.println();
}
}