操作系统 银行家算法 Java 实现

1. 银行家算法的基本原理
2. 代码实现
3. 测试结果截图

操作系统死锁避免——银行家算法

public class SrcAllocTable {
    private int processNum;
    private int sourceNum;
    private Record[] table;
    private int[] sum;
    private int[] available;

    public SrcAllocTable(int[] sum, Record[] table) {
        // if(sum.length != table.length)
        //     throw XXXException;
        this.sum = sum;
        this.table = table;
        this.processNum = table.length;
        this.sourceNum = sum.length;
        this.available = sum.clone();
        for(int i = 0; i 
2). 银行家类（实现银行家算法） 
public class Banker {
    private SrcAllocTable srcTable;

    public Banker(SrcAllocTable table) {
        this.srcTable = table;
    }
	
	
	
    public boolean securityDetect(int i, int[] request) {
        boolean isSecurity = false;

        // 先复制整张资源分配表
        SrcAllocTable tmpTable = new SrcAllocTable(srcTable);
        showDebugInfo("Before allocation: ", tmpTable);

        // 1. 试探性分配资源
        Record[] table = tmpTable.getTable();
        int[] need = table[i].getNeed();
        int[] available = tmpTable.getAvailable();
        int[] allocated = table[i].getAllocation();
        for (int k = 0; k < request.length; k++) {
            need[k] -= request[k];
            available[k] -= request[k];
            allocated[k] += request[k];
        }

        showDebugInfo("After allocation: ", tmpTable);

        int procCount = 0;
        StringBuilder procQueue = new StringBuilder();
        int procNum = tmpTable.getProcessNum(); // 尚未完成的进程或者说表中 isFinished 为 false 的记录的数量
        int srcNum = tmpTable.getSourceNum(); // 资源种类数

        for(int n = 0; n need[k] || request[k] > available[k]) {
                System.out.println("Sorry, the requested source may out of needed or available source!");
                return false;
            }

        // 3. security Detect
        return securityDetect(i, request);
    }

	// 打印资源分配表的情况
    public void showDebugInfo(String info, SrcAllocTable tmpTable){
        System.out.println(info);
        System.out.println(tmpTable);
        System.out.println("------------------------------------------");

    }

    public static void main(String[] args) {
        int[] max0 = {7, 5, 3};
        int[] allocation0 = {0, 1, 0};
        Record r0 = new Record("p0", max0, allocation0);

        int[] max1 = {3, 2, 2};
        int[] allocation1 = {2, 0, 0};
        Record r1 = new Record("p1", max1, allocation1);

        int[] max2 = {9, 0, 2};
        int[] allocation2 = {3, 0, 2};
        Record r2 = new Record("p2", max2, allocation2);

        int[] max3 = {2, 2, 2};
        int[] allocation3 = {2, 1, 1};
        Record r3 = new Record("p3", max3, allocation3);

        int[] max4 = {4, 3, 3};
        int[] allocation4 = {0, 0, 2};
        Record r4 = new Record("p4", max4, allocation4);

        Record[] table = {r0, r1, r2, r3, r4};
        int[] sum = {10, 5, 7};
        SrcAllocTable st = new SrcAllocTable(sum, table);
        System.out.println(st);

        // Banker
        Banker banker = new Banker(st);


        int i = 1;
        int[] request = {1, 0, 2};

        System.out.println(banker.ifAllocate(i, request));
    }
}

 
3. 测试结果：