银行家算法
作者：互联网
操作系统实验报告（银行家算法）
1.实验目的
掌握银行家算法，加深对避免死锁的理解
2.实验内容及要求
实现下列要求，并写出实验报告：（题目、目的、内容和要求、实验原理、程序清单、运行情况（输入输出）、总结。）
系统中有进程P0、P1、P2、P3、P4，三种资源数量分别为A=10、B=5、C=7，T0时刻资源情况如下：
（1）、分析T0时刻安全性，输出分析结果，若安全输出安全序列。
（1）、输入P1提出请求：Requestp1（1，0，2）用银行家算法分析这个请求是否可满足，输出分析结果。若可满足，输出系统安全序列。
实验源代码如下
package com.xiaole.os123.chap01;
import java.util.Scanner;
class Banker {
private String processer[] = { "p0", "p1", "p2", "p3", "p4" };
private int available[] = new int[3];
private int allocation[][] = new int[5][3];
private int need[][] = new int[5][3];
private int work[] = new int[3];
private int request[] = new int[3];
private boolean finish[] = new boolean[5];
private int safeSeries[] = new int[5];
// private int request[][][];
public void Input() {
Scanner scanner = new Scanner(System.in);
for (int i = 0; i < 5; i++) {
System.out.println("请输入进程" + processer[i] + "已获得的三类资源个数：");
for (int j = 0; j < 3; j++) {
allocation[i][j] = scanner.nextInt();
}
}
for (int i = 0; i < 5; i++) {
System.out.println("请输入进程" + processer[i] + "还需要的三类资源个数：");
for (int j = 0; j < 3; j++) {
need[i][j] = scanner.nextInt();
}
}
for (int i = 0; i < 3; i++) {
System.out.println("请输入资源" + processer[i] + "的可用资源量：");
available[i] = scanner.nextInt();
}
}
public int[][] printAllocation() {
System.out.println("Allocation:");
for (int i = 0; i < 5; i++) {
System.out.println();
System.out.print("P"+i+": ");
for (int j = 0; j < 3; j++) {
System.out.print(allocation[i][j] + " ");
}
}
return allocation;
}
public int[][] printNeed() {
System.out.println();
System.out.println("Need:");
for (int i = 0; i < 5; i++) {
System.out.println();
System.out.print("P"+i+": ");
for (int j = 0; j < 3; j++) {
System.out.print(need[i][j] + " ");
}
}
return need;
}
public int[] printAvailable() {
System.out.println();
System.out.println("Available:");
for (int i = 0; i < 3; i++) {
System.out.println("P" + i + ": " + available[i]);
}
return available;
}
public boolean isAllZero(int Kang) { // 判断一个进程资源是否全为零
int num = 0;
for (int i = 0; i < 3; i++) {
if (need[Kang][i] == 0) {
num++;
}
}
if (num == 3) {
return true;
} else {
return false;
}
}
//打印安全检查信息
public void SafeInfo(int work[], int i)
{
int j;
System.out.print("P"+i+" ");
for(j = 0; j < 3; j++)
{
System.out.print(work[j]+" ");
}
System.out.print(" ");
for(j = 0; j < 3; j++)
{
System.out.print(allocation[i][j]+" ");
}
System.out.print(" ");
for(j = 0; j < 3; j++)
{
System.out.print(need[i][j]+" ");
}
System.out.print(" ");
for(j = 0; j < 3; j++)
{
System.out.print(allocation[i][j]+work[j]+" ");
}
System.out.println();
}
public boolean SecurityAlgorithm() { // 安全性算法
// int resourceNumFinish = 0;
int safeIndex = 0;
int allFinish = 0;
int r = 0;
int temp = 0;
int pNum = 0;
int num = 0;
// 预分配为了保护available[]
for (int i = 0; i < 3; i++) {
work[i] = available[i];
}
// 把未完成进程置为false
for (int i = 0; i < 5; i++) {
boolean result = isAllZero(i);
if (result == true) {
finish[i] = true;
allFinish++;
} else {
finish[i] = false;
}
}
// 预分配开始
System.out.println("PID "+"Work "+"Allocation "+"Need "+"Work+Allocation ");
while (allFinish != 5) {
num = 0;
for (int i = 0; i < 3; i++) {
if (need[r][i] <= work[i] && finish[r] == false) {
num++;
}
}
if (num == 3) {
for (int i = 0; i < 3; i++) {
work[i] = work[i] + allocation[r][i];
}
allFinish++;
SafeInfo(work,r);
safeSeries[safeIndex] = r;
safeIndex++;
finish[r] = true;
}
r++;
if (r >= 5) {
r = r % 5;
if (temp == allFinish) {
break;
}
temp = allFinish;
}
pNum = allFinish;
}
// 判断系统是否安全
for (int i = 0; i < 5; i++) {
if (finish[i] == false) {
System.out.print("\n当前系统不安全！故不分配资源");
return false;
}
}
// 打印安全序列
System.out.println("当前系统安全！\n安全序列为：");
for (int i = 0; i < 5; i++) {
boolean result = isAllZero(i);
if (result == true) {
pNum--;
}
}
for (int i = 0; i < pNum; i++) {
System.out.print("P" + safeSeries[i] + "->");
}
return true;
}
public void setRequest() {
Scanner scanner = new Scanner(System.in);
System.out.println();
System.out.println("请输入要分配资源的进程(0-5)：");
int curProcess = scanner.nextInt();
System.out.println("请输入请求的三种资源的个数");
for (int i = 0; i < 3; i++) {
request[i] = scanner.nextInt();
}
int num = 0;
for (int i = 0; i < 3; i++) {
if (request[i] <= need[curProcess][i] && request[i] <= available[i]) {
num++;
} else {
System.out.println("发生错误！可能原因如下：(1)您请求分配的资源可能打于该进程的某些资源的最大需求(2)系统所剩的资源已不足");
break;
}
}
if (num == 3) {
num = 0;
for (int i = 0; i < 3; i++) {
// 分配资源
available[i] = available[i] - request[i];
allocation[curProcess][i] = allocation[curProcess][i] + request[i];
need[curProcess][i] = need[curProcess][i] - request[i];
// 记录分配以后，是否该进程需要值为0了
if (need[curProcess][i] == 0) {
num++;
}
}
// 预分配完成以后，判断该系统是否安全，若安全，则可继续进行分配，若不安全，将已经分配的资源换回来
if (!SecurityAlgorithm()) {
for (int j = 0; j < 3; j++) {
available[j] = available[j] + request[j];
allocation[curProcess][j] = allocation[curProcess][j] - request[j];
need[curProcess][j] = need[curProcess][j] + request[j];
}
System.out.println("资源不足，等待中...\n分配失败！");
}
}
scanner.close();
}
}
public class Demo1 {
public static void main(String[] args) {
Banker bank = new Banker();
bank.Input();
bank.printAllocation();
bank.printNeed();
bank.printAvailable();
bank.SecurityAlgorithm();
bank.setRequest();
}
}
实验截图
有欠妥当的地方还望大家多多斧正
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标签：int,print,System,++,算法,println,银行家,out 来源： https://blog.csdn.net/qq_43775034/article/details/104105168