银行家算法 Java 代码实现240

银行家算法是一种用于解决资源分配问题的算法。在操作系统和计算机科学中，它是一个避免死锁的算法。它通过跟踪系统中可用的资源数量以及每个进程请求的资源数量来工作。

银行家算法由以下步骤组成：1. 初始化：分配可用的资源和进程请求的资源。
2. 安全状态检查：检查系统是否处于安全状态，即是否有可能为所有进程分配资源而不会导致死锁。
3. 资源分配：如果系统处于安全状态，则为进程分配资源。
4. 进程完成：当进程完成时，释放它持有的资源。

以下是银行家算法的 Java 代码实现：```java
import ;
public class BankersAlgorithm {
private int[][] maxResources; // Maximum resources needed by each process
private int[][] allocatedResources; // Resources allocated to each process
private int[] availableResources; // Available resources in the system
private int[][] need; // Resources needed by each process (max - allocated)
private int processCount; // Number of processes
public BankersAlgorithm(int processCount, int resourceCount) {
= processCount;
maxResources = new int[processCount][resourceCount];
allocatedResources = new int[processCount][resourceCount];
need = new int[processCount][resourceCount];
availableResources = new int[resourceCount];
}
// Initialize the resources
public void init() {
Scanner scanner = new Scanner();
("Enter the maximum resources for each process:");
for (int i = 0; i < processCount; i++) {
for (int j = 0; j < ; j++) {
maxResources[i][j] = ();
}
}
("Enter the allocated resources for each process:");
for (int i = 0; i < processCount; i++) {
for (int j = 0; j < ; j++) {
allocatedResources[i][j] = ();
}
}
("Enter the available resources:");
for (int i = 0; i < ; i++) {
availableResources[i] = ();
}
// Calculate the need matrix
for (int i = 0; i < processCount; i++) {
for (int j = 0; j < ; j++) {
need[i][j] = maxResources[i][j] - allocatedResources[i][j];
}
}
}
// Check if the system is in a safe state
public boolean isSafe() {
int[] work = new int[]; // Work vector
for (int i = 0; i < ; i++) {
work[i] = availableResources[i];
}
boolean[] finish = new boolean[processCount]; // Finish vector
for (int i = 0; i < processCount; i++) {
finish[i] = false;
}
int count = 0; // Number of processes finished
while (count < processCount) {
boolean found = false;
for (int i = 0; i < processCount; i++) {
if (!finish[i]) {
boolean canFinish = true;
for (int j = 0; j < ; j++) {
if (need[i][j] > work[j]) {
canFinish = false;
break;
}
}
if (canFinish) {
for (int j = 0; j < ; j++) {
work[j] += allocatedResources[i][j];
}
finish[i] = true;
count++;
found = true;
break;
}
}
}
if (!found) {
return false; // The system is not in a safe state
}
}
return true; // The system is in a safe state
}
// Allocate resources to a process
public void allocate(int processId, int[] request) {
for (int i = 0; i < ; i++) {
if (request[i] > need[processId][i]) {
("Invalid request: Request exceeds need");
return;
}
if (request[i] > availableResources[i]) {
("Invalid request: Request exceeds available resources");
return;
}
}
for (int i = 0; i < ; i++) {
allocatedResources[processId][i] += request[i];
need[processId][i] -= request[i];
availableResources[i] -= request[i];
}
if (isSafe()) {
("Resources allocated successfully");
} else {
("Resources cannot be allocated: System is not in a safe state");
}
}
// Release resources held by a process
public void release(int processId, int[] release) {
for (int i = 0; i < ; i++) {
if (release[i] > allocatedResources[processId][i]) {
("Invalid release: Release exceeds allocated resources");
return;
}
}
for (int i = 0; i < ; i++) {
allocatedResources[processId][i] -= release[i];
need[processId][i] += release[i];
availableResources[i] += release[i];
}
("Resources released successfully");
}
public static void main(String[] args) {
BankersAlgorithm bankersAlgorithm = new BankersAlgorithm(5, 3);
();
// Print the initial state
("Initial state:");
("Max resources:");
for (int[] maxResource : ) {
for (int i : maxResource) {
(i + " ");
}
();
}
("Allocated resources:");
for (int[] allocatedResource : ) {
for (int i : allocatedResource) {
(i + " ");
}
();
}
("Available resources:");
for (int availableResource : ) {
(availableResource + " ");
}
();
// Check if the system is in a safe state
if (()) {
("System is in a safe state");
} else {
("System is not in a safe state");
}
// Allocate resources to a process
int[] request = {1, 0, 2};
(0, request);
// Release resources held by a process
int[] release = {0, 1, 0};
(1, release);
}
}
```