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import java.io.*;
public class bank
{
int MAX_PROCESS = 5; //最大进程数
int MAX_COURCE = 3; //最大资源类别
int[] Available=new int[MAX_COURCE]; //可利用资源向量
int[][] Max= new int[MAX_PROCESS][MAX_COURCE]; //最大需求矩阵
int[][] Allocation=new int[MAX_PROCESS][MAX_COURCE]; //分配矩阵
int[][] Need=new int[MAX_PROCESS][MAX_COURCE]; //需求矩阵
int Request_PROCESS; //发出请求的进程
int[][] Request_COURCE = new int[MAX_PROCESS][MAX_COURCE]; //线程请求资源的数量
public bank()
{
}
public void InitState()
{
System.out.println("初始化当前状态......");
Max[0][0] = 7;Max[0][1] = 5;Max[0][2] = 3;
Allocation[0][0] = 0;Allocation[0][1] = 1;Allocation[0][2] = 0;
Need[0][0] = 7;Need[0][1] = 4;Need[0][2] = 3;
//初始化进程二
Max[1][0] = 3;Max[1][1] = 2;Max[1][2] = 2;
Allocation[1][0] = 2;Allocation[1][1] = 0;Allocation[1][2] = 0;
Need[1][0] = 1;Need[1][1] = 2;Need[1][2] = 2;
//初始化进程三
Max[2][0] = 9;Max[2][1] = 0;Max[2][2] = 2;
Allocation[2][0] = 3;Allocation[2][1] = 0;Allocation[2][2] = 2;
Need[2][0] = 6;Need[2][1] = 0;Need[2][2] = 0;
//初始化进程四
Max[3][0] = 2;Max[3][1] = 2;Max[3][2] = 2;
Allocation[3][0] = 2;Allocation[3][1] = 1;Allocation[3][2] = 1;
Need[3][0] = 0;Need[3][1] = 1;Need[3][2] = 1;
//初始化进程五
Max[4][0] = 4;Max[4][1] = 3;Max[4][2] = 3;
Allocation[4][0] = 0;Allocation[4][1] = 0;Allocation[4][2] = 2;
Need[4][0] = 4;Need[4][1] = 3;Need[4][2] = 1;
//初始化可用资源
Available[0] = 3;Available[1] = 3;Available[2] = 2;
}
public void bankmethod()
{
try
{
System.out.println("请输入请求资源的进程(0-4)：");
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
Request_PROCESS = Integer.parseInt(reader.readLine());
System.out.println("请输入请求资源的数量：");
for(int i=0;i<MAX_COURCE;i++)
{
Request_COURCE[Request_PROCESS][i] = Integer.parseInt(reader.readLine());
}
}catch(IOException e){}
for(int i=0;i<MAX_COURCE;i++)
{
//判断Request<=Need
if( Request_COURCE[Request_PROCESS][i] > Need[Request_PROCESS][i])
{
System.out.println("请求资源大于需求，输入错误。:");
return;
}
//判断Request<=Available
if(Request_COURCE[Request_PROCESS][i] > Available[i])
{
System.out.println("请求资源大于可用资源,此进程进入等待状态。");
System.out.println("请继续下一进程........");
return;
}
}
//修改Available， Allocation， Need
for(int i=0;i<MAX_COURCE;i++)
{
Available[i] = Available[i] - Request_COURCE[Request_PROCESS][i];
Allocation[Request_PROCESS][i] = Allocation[Request_PROCESS][i] + Request_COURCE[Request_PROCESS][i];
Need[Request_PROCESS][i] = Need[Request_PROCESS][i] - Request_COURCE[Request_PROCESS][i];
}
if(IsSafe()) //判断当前状态是否是安全状态
{
System.out.println("系统仍处于安全状态，请求资源成功。");
System.out.println("请继续........");
}
else
{
//非安全状态
System.out.println("系统进入不安全状态，请求资源失败。");
for(int i=0;i<MAX_COURCE;i++)
{
Available[i] = Available[i] + Request_COURCE[Request_PROCESS][i];
Allocation[Request_PROCESS][i] = Allocation[Request_PROCESS][i] - Request_COURCE[Request_PROCESS][i];
Need[Request_PROCESS][i] = Need[Request_PROCESS][i] + Request_COURCE[Request_PROCESS][i];
}
System.out.println("请继续........");
}
}
public boolean IsSafe()
{
int[] work = new int[3];
boolean[] Finish = {false,false,false,false,false};
for(int i=0;i<MAX_COURCE;i++)
{
work[i] = Available[i];
}
//寻找满足Finish[i]=false,Need[i,j]<=Work[j]的进程
int i = 0;
do
{
boolean flag = true;
//是否Need[i][j]<=work[j]
for(int j=0;j<MAX_COURCE;j++)
{
if(Need[i][j]>work[j])
{
flag = false;
break;
}
}
//是否Finish[i]=false且Need[i,j]<=Work[j]
if(Finish[i]==false && flag)
{
for(int j=0;j<MAX_COURCE;j++)
{
work[j] = work[j] + Allocation[i][j];
}
Finish[i] = true;
i = -1; //重新遍历未结束的进程
}
}while(++i<MAX_PROCESS);
i = 0;
while(Finish[i]==true)
{
if(i == 4) return true; //是安全状态，返回true
i++;
}
return false; //非安全状态，返回false
}
/**
* @param args the command line arguments
*/
public static void main(String[] args)
{
bank mybank = new bank();
mybank.InitState();
while(true)
{
mybank.bankmethod();
}
}
} |
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原文链接:https://blog.51cto.com/maple/55189
程序猿的技术大观园：www.javathinker.net
[这个贴子最后由 flybird 在 2020-03-20 11:28:18 重新编辑]
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Java技术网站 → 『 Java开发技术 』 → 『 数据结构和算法专题 』 → 银行家算法范例
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