银行家算法代码,java
时间: 2023-06-28 12:09:41 浏览: 37
以下是Java实现的银行家算法代码,供参考:
```java
public class BankerAlgorithm {
private int numOfProcesses; // 进程数量
private int numOfResources; // 资源数量
private int[] available; // 可用资源数
private int[][] max; // 最大需求矩阵
private int[][] allocation; // 分配矩阵
private int[][] need; // 需求矩阵
public BankerAlgorithm(int numOfProcesses, int numOfResources, int[] available, int[][] max, int[][] allocation) {
this.numOfProcesses = numOfProcesses;
this.numOfResources = numOfResources;
this.available = available.clone();
this.max = new int[numOfProcesses][numOfResources];
this.allocation = new int[numOfProcesses][numOfResources];
this.need = new int[numOfProcesses][numOfResources];
for (int i = 0; i < numOfProcesses; i++) {
for (int j = 0; j < numOfResources; j++) {
this.max[i][j] = max[i][j];
this.allocation[i][j] = allocation[i][j];
this.need[i][j] = max[i][j] - allocation[i][j];
}
}
}
public boolean isSafe() {
boolean[] finish = new boolean[numOfProcesses];
int[] work = available.clone();
while (true) {
boolean flag = false;
for (int i = 0; i < numOfProcesses; i++) {
if (!finish[i] && isLessThanOrEqual(need[i], work)) {
for (int j = 0; j < numOfResources; j++) {
work[j] += allocation[i][j];
}
finish[i] = true;
flag = true;
}
}
if (!flag) {
break;
}
}
for (int i = 0; i < numOfProcesses; i++) {
if (!finish[i]) {
return false;
}
}
return true;
}
public boolean requestResources(int pid, int[] request) {
if (!isLessThanOrEqual(request, need[pid])) {
return false; // 请求超过了需要的资源数
}
if (!isLessThanOrEqual(request, available)) {
return false; // 当前没有足够的资源可供分配
}
for (int i = 0; i < numOfResources; i++) {
available[i] -= request[i];
allocation[pid][i] += request[i];
need[pid][i] -= request[i];
}
if (!isSafe()) {
// 恢复现场
for (int i = 0; i < numOfResources; i++) {
available[i] += request[i];
allocation[pid][i] -= request[i];
need[pid][i] += request[i];
}
return false;
}
return true;
}
private boolean isLessThanOrEqual(int[] a, int[] b) {
for (int i = 0; i < a.length; i++) {
if (a[i] > b[i]) {
return false;
}
}
return true;
}
}
```
使用时,可以按照以下步骤进行:
1. 初始化银行家算法对象时,传入进程数量、资源数量、可用资源数、最大需求矩阵和分配矩阵;
2. 调用 `isSafe()` 方法判断当前状态是否安全,如果返回 `true`,则说明系统处于安全状态,否则说明系统处于不安全状态;
3. 当某个进程需要请求一定数量的资源时,调用 `requestResources()` 方法传入进程编号和资源请求数组,如果请求成功,则返回 `true`,否则返回 `false`。
需要注意的是,这里的资源数、最大需求矩阵和分配矩阵都是以数组或矩阵的形式传入的,因此需要在使用时先将其转化为相应的数组或矩阵形式。