Java银行家算法

package 银行家算法;


import javax.swing.JOptionPane;


public class Bank {
// 每个进程所需要的最大资源数
public static int MAX[][] = { { 7, 5, 3 }, { 3, 2, 2 }, { 9, 0, 2 },
{ 2, 2, 2 }, { 4, 3, 3 } };
// 系统拥有的初始资源数
public static int AVAILABLE[] = { 10, 5, 7 };
// 系统已给每个进程分配的资源数
public static int ALLOCATION[][] = { { 0, 0, 0 }, { 0, 0, 0 }, { 0, 0, 0 },
{ 0, 0, 0 }, { 0, 0, 0 } };
// 每个进程还需要的资源数
public static int NEED[][] = { { 7, 5, 3 }, { 3, 2, 2 }, { 9, 0, 2 },
{ 2, 2, 2 }, { 4, 3, 3 } };
// 每次申请的资源数
public static int Request[] = { 0, 0, 0 };
// 进程数与资源数
public static int M = 5, N = 3;
int FALSE = 0;
int TRUE = 1;


public void showdata() {
int i, j;
System.out.print("系统可用的资源数为:/n");
for (j = 0; j < N; j++) {
System.out.print("资源" + j + ":" + AVAILABLE[j] + " ");
}
System.out.println();
System.out.println("各进程还需要的资源量:");
for (i = 0; i < M; i++) {
System.out.print("进程" + i + ":");
for (j = 0; j < N; j++) {
System.out.print("资源" + j + ":" + NEED[i][j] + " ");
}
System.out.print("/n");
}
System.out.print("各进程已经得到的资源量: /n");
for (i = 0; i < M; i++) {
System.out.print("进程");
System.out.print(i);
for (j = 0; j < N; j++) {
System.out.print("资源" + j + ":" + ALLOCATION[i][j] + " ");
}
System.out.print("/n");
}
}


// 分配资源，并重新更新各种状态
public void changdata(int k) {
int j;
for (j = 0; j < N; j++) {
AVAILABLE[j] = AVAILABLE[j] - Request[j];
ALLOCATION[k][j] = ALLOCATION[k][j] + Request[j];
NEED[k][j] = NEED[k][j] - Request[j];
}
};


// 回收资源，并重新更新各种状态
public void rstordata(int k) {
int j;
for (j = 0; j < N; j++) {
AVAILABLE[j] = AVAILABLE[j] + Request[j];
ALLOCATION[k][j] = ALLOCATION[k][j] - Request[j];
NEED[k][j] = NEED[k][j] + Request[j];
}
};


// 释放资源
public void free(int k) {
for (int j = 0; j < N; j++) {
AVAILABLE[j] = AVAILABLE[j] + ALLOCATION[k][j];
System.out.print("释放" + k + "号进程的" + j + "资源!/n");
}
}


public int check0(int k) {
int j, n = 0;
for (j = 0; j < N; j++) {
if (NEED[k][j] == 0)
n++;
}
if (n == 3)
return 1;
else
return 0;
}


// 检查安全性函数
public int chkerr(int s) {
int WORK;
int FINISH[] = new int[M], temp[] = new int[M];// 保存临时的安全进程序列
int i, j, k = 0;
for (i = 0; i < M; i++)
FINISH[i] = FALSE;
for (j = 0; j < N; j++) {
WORK = AVAILABLE[j]; // 第j个资源可用数
i = s;
// 判断第i个进程是否满足条件
while (i < M) {
if (FINISH[i] == FALSE && NEED[i][j] <= WORK) {
WORK = WORK + ALLOCATION[i][j];
FINISH[i] = TRUE;
temp[k] = i;
k++;
i = 0;
} else {
i++;
}
}
for (i = 0; i < M; i++)
if (FINISH[i] == FALSE) {
System.out.print("/n系统不安全!!! 本次资源申请不成功!/n");
return 1;
}
}
System.out.print("/n经安全性检查，系统安全，本次分配成功。/n");
System.out.print("本次安全序列：");
for (i = 0; i < M - 1; i++) {
System.out.print("进程" + temp[i] + "->");
}
System.out.print("进程" + temp[M - 1]);
System.out.println("/n");
return 0;
}


/**
* @param args
*/
public static void main(String[] args) {
int i = 0, j = 0;
int flag = 1;
Bank bank = new Bank();
bank.showdata();
while (flag == 1) {
i = -1;
while (i < 0 || i >= M) {
String str = JOptionPane.showInputDialog("请输入需申请资源的进程号（从0到"
+ (M - 1) + "，否则重输入!）");
i = Integer.parseInt(str);
if (i < 0 || i >= M)
System.out.println("输入的进程号不存在，重新输入!/n");
}
System.out.print("请输入进程" + i + "申请的资源数/n");
for (j = 0; j < N; j++) {
String str = JOptionPane.showInputDialog("资源" + j + ":");
Request[j] = Integer.parseInt(str);
if (Request[j] > NEED[i][j]) {
System.out.print("进程" + i + "申请的资源数大于进程" + i + "还需要" + j
+ "类资源的资源量!申请不合理，出错!请重新选择!/n");
flag = 0;
break;
} else {
if (Request[j] > AVAILABLE[j]) {
System.out.print("进程" + i + "申请的资源数大于系统可用" + j
+ "类资源的资源量!申请不合理，出错!请重新选择!/n");
flag = 0;
break;
}
}
}
if (flag == 1) {
bank.changdata(i);
int chkerr = bank.chkerr(i);
if (chkerr == 1) {
bank.rstordata(i);
bank.showdata();
} else {
bank.showdata();
int check = bank.check0(i);
if (check == 1) {
System.out.print("进程" + i + "已经完成，系统将其所占用资源释放/n");
bank.free(i);
}
}
} else {
bank.showdata();
}
System.out.println("/n");
String str = JOptionPane
.showInputDialog("是否继续银行家算法演示,按'1'键继续,按'0'键退出演示");
flag = Integer.parseInt(str);
}
}
}