死锁避免系统java实现

死锁避免是一种预防死锁的策略，在资源申请时通过安全性检查来避免系统进入死锁状态。下面是一个简单的Java实现：

public class DeadlockAvoidanceSystem {
    private int[][] allocation;
    private int[][] max;
    private int[] available;
    private int[] work;
    private boolean[] finish;

    public DeadlockAvoidanceSystem(int[][] allocation, int[][] max, int[] available) {
        this.allocation = allocation;
        this.max = max;
        this.available = available;
        this.work = available.clone();
        this.finish = new boolean[allocation.length];
    }

    public boolean requestResources(int processId, int[] request) {
        if (lessEqual(request, need(processId)) && lessEqual(request, available)) {
            // 试探性地分配资源
            for (int i = 0; i < request.length; i++) {
                allocation[processId][i] += request[i];
                available[i] -= request[i];
                need(processId)[i] -= request[i];
            }
            // 检查是否安全
            if (isSafe()) {
                return true;
            } else {
                // 回滚分配
                for (int i = 0; i < request.length; i++) {
                    allocation[processId][i] -= request[i];
                    available[i] += request[i];
                    need(processId)[i] += request[i];
                }
            }
        }
        return false;
    }

    private boolean isSafe() {
        for (int i = 0; i < allocation.length; i++) {
            finish[i] = false;
        }
        int count = 0;
        while (count < allocation.length) {
            boolean find = false;
            for (int i = 0; i < allocation.length; i++) {
                if (!finish[i] && lessEqual(need(i), work)) {
                    find = true;
                    for (int j = 0; j < work.length; j++) {
                        work[j] += allocation[i][j];
                    }
                    finish[i] = true;
                    count++;
                }
            }
            if (!find) {
                return false; // 找不到满足条件的进程，说明不安全
            }
        }
        return true;
    }

    private int[] need(int processId) {
        int[] need = new int[max[processId].length];
        for (int i = 0; i < max[processId].length; i++) {
            need[i] = max[processId][i] - allocation[processId][i];
        }
        return need;
    }

    private boolean lessEqual(int[] a, int[] b) {
        for (int i = 0; i < a.length; i++) {
            if (a[i] > b[i]) {
                return false;
            }
        }
        return true;
    }
}

使用时，可以按照以下步骤：

1. 定义进程数、资源数、分配矩阵、最大需求矩阵和可用资源向量。
2. 创建`DeadlockAvoidanceSystem`对象，传入上述参数。
3. 调用`requestResources()`方法来申请资源，如果返回true，则表示申请成功，否则失败。

示例代码：

public static void main(String[] args) {
    int[][] allocation = {{0, 1, 0}, {2, 0, 0}, {3, 0, 2}, {2, 1, 1}, {0, 0, 2}};
    int[][] max = {{7, 5, 3}, {3, 2, 2}, {9, 0, 2}, {2, 2, 2}, {4, 3, 3}};
    int[] available = {3, 3, 2};

    DeadlockAvoidanceSystem system = new DeadlockAvoidanceSystem(allocation, max, available);
    int[] request = {0, 0, 2};
    if (system.requestResources(2, request)) {
        System.out.println("Request success!");
    } else {
        System.out.println("Request failed!");
    }
}

注意：这只是一个简单的死锁避免系统的实现，实际上死锁避免是一个很复杂的问题，在实际应用中还需要考虑许多因素，如系统资源的动态分配、进程优先级等。