本文已参与「新人创作礼」活动，一起开启掘金创作之路。
关于银行家算法，是操作系统进程分配中很重要的一个算法，理论解释请看这篇文章
blog.csdn.net/Mr_YanMingX…
在这里用Java做一下简单代码的实现：
/**
* Java实现银行家算法
*
* @author 17122
*/
public class Test01 {
/**
* 数据结构
*/
public int[][] allocation;
public int[][] need;
public int[] available;
/**
* 初始化方法
*/
public void init() {
allocation = new int[][]{
{0, 0, 3, 2},
{1, 0, 0, 0},
{1, 3, 5, 4},
{0, 3, 3, 2},
{0, 0, 1, 4}
};
need = new int[][]{
{0, 0, 1, 2},
{1, 7, 5, 0},
{2, 3, 5, 6},
{0, 6, 5, 2},
{0, 6, 5, 6}
};
available = new int[]{1, 6, 2, 2};
System.out.println("Allocation矩阵： Need矩阵： Available：");
for (int i = 0; i < allocation.length; i++) {
for (int j = 0; j < allocation[i].length; j++) {
System.out.print(allocation[i][j] + " ");
}
System.out.print(" ");
for (int j = 0; j < need[i].length; j++) {
System.out.print(need[i][j] + " ");
}
if (i == 0) {
System.out.print(" ");
for (int j = 0; j < available.length; j++) {
System.out.print(available[j] + " ");
}
}
System.out.println();
}
}
/**
* 请求资源方法
*
* @param index 请求的进程
* @param req 请求数量
*/
public void request(int index, int[] req) {
//先进性数据初始化
init();
if (req[0] <= available[0] && req[1] <= available[1] && req[2] <= available[2] && req[3] <= available[3]) {
//分配
int[] process_has = allocation[index];
int[] process_need = need[index];
if (process_need[0] >= req[0] && process_need[1] >= req[1] && process_need[2] >= req[2] && process_need[3] >= req[3]) {
for (int i = 0; i < process_has.length; i++) {
process_has[i] += req[i];
process_need[i] -= req[i];
}
for (int i = 0; i < available.length; i++) {
available[i] -= req[i];
}
}
//检查
if (safe()) {
System.out.println("分配成功！");
} else {
System.out.println("分配后不安全，取消分配！");
}
} else {
System.out.println("可用资源不足，无法分配！");
}
}
/**
* 检查方法
*
* @return
*/
public boolean safe() {
Boolean[] finish = {false, false, false, false, false};
// 完成进程数
int count = 0;
// 循环圈数
int circle = 0;
// 安全序列
int[] S = new int[5];
// 设置工作向量
int work[] = available;
boolean flag = true;
boolean isNeed = true;
while (count < 5) {
if (flag) {
System.out.println("Process " + " Work " + " Allocation " + " Need " + " Available ");
flag = false;
}
for (int i = 0; i < 5; i++) {
isNeed = true;
for (int j = 0; j < 4; j++) {
if (!(finish[i] == false && need[i][j] <= work[j])) {
isNeed = false;
}
}
// 判断条件
if (isNeed) {
System.out.print("P" + i + " ");
for (int k = 0; k < 4; k++) {
System.out.print(work[k] + " ");
}
System.out.print(" ");
for (int j = 0; j < 4; j++) {
work[j] += allocation[i][j];
}
// 当前进程能满足时
finish[i] = true;
// 当前序列
S[count] = i;
// 满足进程数+1
count++;
for (int j = 0; j < 4; j++) {
System.out.print(allocation[i][j] + " ");
}
System.out.print(" ");
for (int j = 0; j < 4; j++) {
System.out.print(need[i][j] + " ");
}
System.out.print(" ");
for (int j = 0; j < 4; j++) {
System.out.print(work[j] + " ");
}
System.out.println();
}
}
// 循环圈数加1
circle++;
// 判断是否满足所有进程需要
if (count == 5) {
System.out.print("安全序列为：");
// 输出安全序列
for (int i = 0; i < 5; i++) {
System.out.print("P" + S[i] + " ");
}
return true;
}
// 判断完成进程数是否小于循环圈数
if (count < circle) {
return false;
}
}
return false;
}
public static void main(String[] args) {
Test01 test01 = new Test01();
test01.request(0, new int[]{0, 0, 1, 2});
}
}
运行结果：
