模拟银行家算法java
时间: 2023-11-01 12:53:47 浏览: 47
银行家算法是一种资源分配的算法,主要用于避免死锁的发生。以下是一个简单的 Java 实现:
```java
import java.util.Scanner;
public class BankersAlgorithm {
private int[][] max; // 最大需求矩阵
private int[][] allocation; // 已分配矩阵
private int[][] need; // 需求矩阵
private int[] available; // 可用资源数组
private int processNum; // 进程数
private int resourceNum; // 资源数
public BankersAlgorithm(int[][] max, int[][] allocation, int[] available) {
this.max = max;
this.allocation = allocation;
this.available = available;
this.processNum = max.length;
this.resourceNum = available.length;
this.need = new int[processNum][resourceNum];
for (int i = 0; i < processNum; i++) {
for (int j = 0; j < resourceNum; j++) {
this.need[i][j] = max[i][j] - allocation[i][j];
}
}
}
// 检查是否满足需求
private boolean check(int process, int[] request) {
for (int i = 0; i < resourceNum; i++) {
if (request[i] > need[process][i] || request[i] > available[i]) {
return false;
}
}
return true;
}
// 请求资源
public boolean request(int process, int[] request) {
if (!check(process, request)) {
return false;
}
for (int i = 0; i < resourceNum; i++) {
available[i] -= request[i];
allocation[process][i] += request[i];
need[process][i] -= request[i];
}
return true;
}
// 释放资源
public void release(int process) {
for (int i = 0; i < resourceNum; i++) {
available[i] += allocation[process][i];
allocation[process][i] = 0;
need[process][i] = 0;
max[process][i] = 0;
}
}
// 执行银行家算法
public boolean execute() {
boolean[] finish = new boolean[processNum];
int[] work = available.clone();
int count = 0;
while (count < processNum) {
boolean flag = false;
for (int i = 0; i < processNum; i++) {
if (!finish[i] && check(i, need[i])) {
flag = true;
for (int j = 0; j < resourceNum; j++) {
work[j] += allocation[i][j];
}
finish[i] = true;
count++;
}
}
if (!flag) {
return false;
}
}
return true;
}
// 打印矩阵
public void printMatrix(int[][] matrix) {
for (int i = 0; i < processNum; i++) {
for (int j = 0; j < resourceNum; j++) {
System.out.print(matrix[i][j] + " ");
}
System.out.println();
}
}
// 打印状态
public void printStatus() {
System.out.println("Max:");
printMatrix(max);
System.out.println("Allocation:");
printMatrix(allocation);
System.out.println("Need:");
printMatrix(need);
System.out.println("Available:");
for (int i = 0; i < resourceNum; i++) {
System.out.print(available[i] + " ");
}
System.out.println();
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("请输入进程数:");
int processNum = scanner.nextInt();
System.out.print("请输入资源数:");
int resourceNum = scanner.nextInt();
int[][] max = new int[processNum][resourceNum];
int[][] allocation = new int[processNum][resourceNum];
int[] available = new int[resourceNum];
System.out.println("请输入 Max 矩阵:");
for (int i = 0; i < processNum; i++) {
for (int j = 0; j < resourceNum; j++) {
max[i][j] = scanner.nextInt();
}
}
System.out.println("请输入 Allocation 矩阵:");
for (int i = 0; i < processNum; i++) {
for (int j = 0; j < resourceNum; j++) {
allocation[i][j] = scanner.nextInt();
}
}
System.out.println("请输入 Available 数组:");
for (int i = 0; i < resourceNum; i++) {
available[i] = scanner.nextInt();
}
BankersAlgorithm banker = new BankersAlgorithm(max, allocation, available);
banker.printStatus();
System.out.println("请输入请求资源的进程编号和请求资源数组(以空格分隔):");
int process = scanner.nextInt();
int[] request = new int[resourceNum];
for (int i = 0; i < resourceNum; i++) {
request[i] = scanner.nextInt();
}
if (banker.request(process, request)) {
if (banker.execute()) {
System.out.println("请求通过,系统处于安全状态");
} else {
banker.release(process);
System.out.println("请求未通过,系统不处于安全状态");
}
} else {
System.out.println("请求未通过,进程需求超过最大需求或资源不足");
}
banker.printStatus();
}
}
```
这个实现可以通过用户的输入来执行银行家算法,并输出相关的矩阵和状态信息。注意,这只是一个简单的实现,实际应用中需要考虑更多的因素。