基于Java页面置换算法的模拟实现

好的，以下是基于Java的页面置换算法的模拟实现：

import java.util.ArrayList;
import java.util.Arrays;

public class PageReplacementSimulator {
    private int[] pageRequests; // 页面请求序列
    private int[] pageFrames; // 页面帧序列
    private int pageFaults; // 页面错误次数
    private String algorithm; // 页面置换算法

    public PageReplacementSimulator(int[] pageRequests, int[] pageFrames, String algorithm) {
        this.pageRequests = pageRequests;
        this.pageFrames = pageFrames;
        this.algorithm = algorithm;
    }

    public void simulate() {
        switch (algorithm) {
            case "FIFO":
                simulateFIFO();
                break;
            case "LRU":
                simulateLRU();
                break;
            case "OPT":
                simulateOPT();
                break;
            default:
                System.out.println("Unsupported algorithm");
                break;
        }
    }

    private void simulateFIFO() {
        ArrayList<Integer> queue = new ArrayList<>();
        pageFaults = 0;

        for (int pageRequest : pageRequests) {
            if (!queue.contains(pageRequest)) {
                pageFaults++;

                if (queue.size() == pageFrames.length) {
                    queue.remove(0);
                }

                queue.add(pageRequest);
            }
        }

        System.out.println("FIFO: " + pageFaults + " page faults");
    }

    private void simulateLRU() {
        ArrayList<Integer> list = new ArrayList<>();
        pageFaults = 0;

        for (int pageRequest : pageRequests) {
            if (!list.contains(pageRequest)) {
                pageFaults++;

                if (list.size() == pageFrames.length) {
                    list.remove(0);
                }
            } else {
                list.remove(Integer.valueOf(pageRequest));
            }

            list.add(pageRequest);
        }

        System.out.println("LRU: " + pageFaults + " page faults");
    }

    private void simulateOPT() {
        ArrayList<Integer> list = new ArrayList<>();
        pageFaults = 0;

        for (int i = 0; i < pageRequests.length; i++) {
            int pageRequest = pageRequests[i];

            if (!list.contains(pageRequest)) {
                pageFaults++;

                if (list.size() == pageFrames.length) {
                    int[] distances = new int[pageFrames.length];

                    for (int j = 0; j < pageFrames.length; j++) {
                        int index = i + 1;
                        int distance = 0;

                        while (index < pageRequests.length && pageFrames[j] != pageRequests[index]) {
                            index++;
                            distance++;
                        }

                        distances[j] = distance;
                    }

                    int maxIndex = 0;

                    for (int j = 1; j < distances.length; j++) {
                        if (distances[j] > distances[maxIndex]) {
                            maxIndex = j;
                        }
                    }

                    list.remove(Integer.valueOf(pageFrames[maxIndex]));
                }
            }

            list.add(pageRequest);
        }

        System.out.println("OPT: " + pageFaults + " page faults");
    }

    public static void main(String[] args) {
        int[] pageRequests = {1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5};
        int[] pageFrames = {3, 4};

        PageReplacementSimulator simulator = new PageReplacementSimulator(pageRequests, pageFrames, "FIFO");
        simulator.simulate();

        simulator = new PageReplacementSimulator(pageRequests, pageFrames, "LRU");
        simulator.simulate();

        simulator = new PageReplacementSimulator(pageRequests, pageFrames, "OPT");
        simulator.simulate();
    }
}

这个模拟器实现了三种页面置换算法：FIFO、LRU和OPT。用户可以通过构造函数传入页面请求序列、页面帧序列和算法名称，然后调用simulate()方法进行模拟。在模拟过程中，程序会统计页面错误次数，并输出结果。