Fast implementation of FCFS algorithm and SPF algorithm
Let's take a look at the overall structure of the code:
In the process shown in the figure above, the only difference between the FCFS algorithm and the SJF algorithm is the ordering method of the intermediate steps. Therefore, just replace the sorting method in the code.
In this program, the default is the FCFS algorithm, if you need the SPF algorithm, you can open the dequeue()commented method in the sortJcbsByServeTime()method.
The comments in the code are relatively detailed, because it was written earlier, so the design in some places is not particularly good, please understand
Code
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JCB entity class:
package fcfs; import java.text.DecimalFormat; public class JCB { /** * 作业名 */ String name; /** * 到达时间 */ int arriveTime; /** * 服务时间 */ int serveTime; /** * 开始时间 */ int beginTime; /** * 结束时间 */ int finishTime; /** * 周转时间 */ int roundTime; /** * 带权周转时间 */ double aveRoundTime; public JCB() { } public JCB(String name, int arriveTime, int serveTime) { super(); this.name = name; this.arriveTime = arriveTime; this.serveTime = serveTime; } @Override public String toString() { DecimalFormat df = new DecimalFormat("#0.00"); return name + "\t\t" + arriveTime + "\t\t" + serveTime + "\t\t" + beginTime + "\t\t" + finishTime + "\t\t" + roundTime + "\t\t" + df.format(aveRoundTime); } } -
ProcessQueue
package fcfs; import java.text.DecimalFormat; import java.util.ArrayList; import java.util.Collections; import java.util.LinkedList; public class ProcessQueue { //jcbs的下标 int index = 0; //当前的时间 private int currentTime = 0; //所有任务 private ArrayList<JCB> jcbs; //就绪队列 private LinkedList<JCB> ready = new LinkedList(); //执行结束后的结果 private ArrayList<JCB> result = new ArrayList<>(); //平均周转时间 private double avgRoundTime = 0; //周转时间和 private double sumRoundTime = 0; //平均带权周转时间 private double avgAveRoundTime = 0; //带权周转时间和 private double sumAveRoundTime = 0; public ProcessQueue(ArrayList<JCB> jcbs) { this.jcbs = jcbs; //排序（如果是FCFS算法，则不能被注释） sortJcbs(); } /** * 将要做的所有作业按照到达顺序进行排序 */ public void sortJcbs() { Collections.sort(jcbs,(o1, o2) -> { int time = o1.arriveTime - o2.arriveTime; if (time > 0) { return 1; }else if (time == 0) { //到达时间相同就比较服务时间 return o1.serveTime > o2.serveTime ? 1 : -1; }else { return -1; } }); } /** * 用于SJF算法 * 对已到达的作业作业优先按照服务时间进行排序 */ public void sortJcbsByServeTime() { Collections.sort(ready,(o1, o2) -> { int time = o1.serveTime - o2.serveTime; if (time > 0) { return 1; }else if (time == 0) { //到达时间相同就比较服务时间 return o1.arriveTime > o2.arriveTime ? 1 : -1; }else { return -1; } }); } /** * 到达的作业进入就绪队列 */ public void enqueue() { while (index < jcbs.size()) { if (jcbs.get(index).arriveTime <= currentTime) { //出队，index++，避免以及出队的进程重复出队 ready.add(jcbs.get(index)); index++; }else { break; } } } /** * 第一个执行完的作业出队 */ public void dequeue() { if (!ready.isEmpty()) { //如果是（SJF算法，则下面这个方法不能被注释） //sortJcbsByServeTime(); JCB jcb = ready.removeFirst(); //设置出队列后的jcb的属性 jcb.beginTime = currentTime; jcb.finishTime = jcb.beginTime + jcb.serveTime; jcb.roundTime = jcb.finishTime - jcb.arriveTime; jcb.aveRoundTime = (double) jcb.roundTime / jcb.serveTime; //重置当前时间 currentTime = jcb.finishTime; //记录出队列的结果 result.add(jcb); } } /** * 打印当前队列状况 */ public void showReady() { // for (int i = 1; i < ready.size(); i++) { // System.out.println("第" + i + "次队列情况:" + ready); // } StringBuilder stringBuilder = new StringBuilder(); stringBuilder.append("当前已到达的进程的情况："); ready.stream().forEach(r -> { stringBuilder.append(r.name + " "); }); System.out.println(stringBuilder.toString()); } /** * 执行程序 */ public void run() { //当有作业的时候就一直循环 while (index < jcbs.size()) { //出队一个 dequeue(); //让到达的进程入队 enqueue(); //没有作业到达的时候，就等一下 if (ready.isEmpty()) { currentTime++; } } dequeue(); dequeue(); dequeue(); System.out.println("++++++++++++++++++++++执++++++++行++++++++结++++++++果++++++++++++++++++"); System.out.println("作业名" + "\t到达时间" + "\t服务时间" + "\t开始时间" + "\t完成时间" + "\t周转时间" + "\t带权周转时间"); result.stream().forEach(s -> { sumRoundTime += s.roundTime; sumAveRoundTime += s.aveRoundTime; System.out.println(s); }); DecimalFormat df = new DecimalFormat("#0.00"); avgAveRoundTime = sumAveRoundTime/result.size(); avgRoundTime = sumRoundTime/result.size(); System.out.println("平均周转时间：" + df.format(avgRoundTime)); System.out.println("平均带权周转时间 " + df.format(avgAveRoundTime)); } } -
Main function:
package fcfs; import java.util.ArrayList; public class Main { public static void main(String[] args) { //所有任务 ArrayList<JCB> jcbs = new ArrayList<>(); JCB p1 = new JCB("0", 3, 2); JCB p2 = new JCB("1", 1, 2); JCB p3 = new JCB("2", 5, 3); JCB p4 = new JCB("3", 7, 1); jcbs.add(p1); jcbs.add(p2); jcbs.add(p3); jcbs.add(p4); //将任务传入Fcfs程序中运行 ProcessQueue process = new ProcessQueue(jcbs); process.run(); } }
operation result
SPF algorithm:
++++++++++++++++++++++执++++++++行++++++++结++++++++果++++++++++++++++++
作业名 到达时间 服务时间 开始时间 完成时间 周转时间 带权周转时间
1 1 2 1 3 2 1.00
0 3 2 3 5 2 1.00
2 5 3 5 8 3 1.00
3 7 1 8 9 2 2.00
平均周转时间：2.25
平均带权周转时间 1.25
FCFS algorithm:
++++++++++++++++++++++执++++++++行++++++++结++++++++果++++++++++++++++++
作业名 到达时间 服务时间 开始时间 完成时间 周转时间 带权周转时间
2 1 1 1 2 1 1.00
1 3 4 3 7 4 1.00
3 5 1 7 8 3 3.00
平均周转时间：2.67
平均带权周转时间 1.67
Hope to help everyone^-^