实验一进程管理与进程同步

实验目的：

了解进程管理的实现方法，理解和掌握处理进程同步问题的方法。

实验内容：

实现银行家算法、进程调度过程的模拟、读者-写者问题的写者优先算法。

实验步骤：

1.银行家算法流程图

（1）初始化函数init（）

（2）银行家算法Banker（）

（3）安全性算法safe（）

2.银行家算法代码和运行效果图

（1）银行家算法完整代码

//自己设置package

import java.util.Scanner;

//银行家算法

public class Banker {

       Scanner sc=null;

       int resNum=0;

       int proNum=0;

       int res[]=null;

       int[][]max=null;

       int[][]allocation=null;

       int[][]need=null;

       int []available=null;


       void init() {

              sc=new Scanner(System.in);

              System.out.println("输入资源的种类数");

              resNum=sc.nextInt();

              System.out.println("输入进程的数量");

              proNum=sc.nextInt();

              res=new int[resNum];{

                     System.out.println("请分别输入系统"+resNum+"类资源数量：");

                     for(int i=0;i<resNum;i++) {

                            res[i]=sc.nextInt();

                     }

                     }

            

              max=new int[proNum][resNum];{

              System.out.println("请分别输入"+proNum+"个进程所需的"+resNum+"类资源的最大需求数量：");

              for(int j=0;j<proNum;j++) {

                     for(int k=0;k<resNum;k++) {

                            max[j][k]=sc.nextInt();

                            }

                     }

              }

              allocation=new int[proNum][resNum];{//已分配

              System.out.println("请分别输入"+proNum+"个进程,"+resNum+"类资源的已分配情况：");

              for(int l=0;l<5;l++) {

                     for(int m=0;m<resNum;m++) {

                            allocation[l][m]=sc.nextInt();

                            }

                     }

              }

              need=new int[proNum][resNum];{

                     for(int o=0;o<proNum;o++) {

                            for(int p=0;p<resNum;p++) {

                                   need[o][p]=max[o][p]-allocation[o][p];

                            }

                     }

              }

              available=new int[resNum];{

                     for(int i=0;i<resNum;i++) {

                            for(int j=0;j<proNum;j++) {

                                  

                                   res[i]=res[i]-allocation[j][i];

                            }

                            available[i]=res[i];

                                  

                     }

                     }

       }



    void showData() {

           String s="";

           for(int i=0;i<resNum;i++)

                         s=s+"\t";

        System.out.print("进程号"+"\t"+"Max"+s+"All"+s+" Need"+s+"Avai");

        System.out.println();

        System.out.print("\t");

        for(int j=0;j<4;j++) {

               for(int i=0;i<resNum;i++) {

                   System.out.print((char)('A'+i)+"\t");

            }

        }

        System.out.println();

        for(int i = 0;i<proNum;i++){

            System.out.print("P"+i+"\t");

            for(int m = 0;m<resNum;m++) System.out.print(max[i][m]+"\t");

            for(int m = 0;m<resNum;m++) System.out.print(allocation[i][m]+"\t");

            for(int m = 0;m<resNum;m++) System.out.print(need[i][m]+"\t");

            if(i==0)  for(int m = 0;m<resNum;m++) System.out.print(available[m]+"\t");

            System.out.println();

        }

    }


    boolean change(int inRequestNum,int inRequest[])

    {

        int requestNum = inRequestNum;

        int request[] = inRequest;      

        System.out.println();


        boolean f1=true;

        for(int i=0;i<resNum;i++) {

               f1=f1&request[i]<=need[requestNum][i];

               if(!f1) {

                      System.out.print("<===P"+inRequestNum+"进程不满足,Request(");

                        for(int j=0;j<resNum;j++) {

                               System.out.print(inRequest[j]);

                               if(j<resNum-1)

                                      System.out.print(",");

                        }

                        System.out.print(")<=Need(");

                        for(int j=0;j<resNum;j++) {

                               System.out.print(need[requestNum][j]);

                               if(j<resNum-1)

                                      System.out.print(",");

                        }

                        System.out.println("),分配错误！===>");

                        return false;

            }

        }



        boolean f2=true;

        for(int i=0;i<resNum;i++) {

               f2=f2&request[i]<=available[i];

               if(!f2) {

                      System.out.print("<===P"+inRequestNum+"进程不满足,Request(");

                      for(int j=0;j<resNum;j++) {

                             System.out.print(inRequest[i]);

                             if(j<resNum-1)

                                    System.out.print(",");

                             }

                      System.out.print(")<=Available(");

                      for(int j=0;j<resNum;j++) {

                             System.out.print(available[i]);

                             if(j<resNum-1)

                                    System.out.print(",");

                             }

                      System.out.println("),分配错误！===>");

                  

                return false;

               }

        }


        for(int i = 0;i<resNum;i++)

        {

            available[i] = available[i]-request[i];

            allocation[requestNum][i] = allocation[requestNum][i] + request[i];

            need[requestNum][i] = need[requestNum][i] - request[i];

        }


        System.out.println("<===安全性检查前的资源分配表===>");

        showData();

       

        boolean flag = checkSafe(available);

        if(flag==true)

        {

            System.out.println("<===通过安全性算法，能够安全分配!===>");

            System.out.println("<===通过安全性算法的资源分配表!===>");

            showData();

            return true;

        }

        else

        {


            for(int i = 0;i<3;i++)

            {

                available[i] = available[i]+request[i];

                allocation[requestNum][i] = allocation[requestNum][i] - request[i];

                need[requestNum][i] = need[requestNum][i] + request[i];

            }

            System.out.println("<===未通过安全性算法，不能够安全分配!===>");

            System.out.println("<===未通过安全性算法的资源分配表!===>");

            showData();

            return false;

        }

    }

    boolean checkSafe(int res[])

    {

        int work[] = new int[resNum] ;

        for(int i=0 ;i<resNum;i++) {

               work[i]=res[i];

        }

        int i=0;


        String [] str=new String[proNum];

        int x=0;


        boolean finish[] = new boolean[proNum] ;

        for(int j=0;j<proNum;j++)

               finish[j]=false;

        System.out.println("<======进行安全性算法======>");

        while(i<proNum)

        {

               boolean f3=true;

               f3=f3&(finish[i]==false);

               for(int j=0;j<resNum;j++) {

                      f3=f3&(need[i][j]<=work[j]);

               }

            if(f3)

            {

                System.out.println("---P"+i+"进程成功分配---");

                if(x<proNum-1) {

                       str[x]="P"+i+"->";

                }

                else {

                       str[x]="P"+i;

                }

                x++;

                for(int m = 0;m<resNum;m++)

                    work[m] =work[m] + allocation[i][m];

                       finish[i] = true;

                       i=0;

            }

            else

                i++;

               }

        for(i=0;i<proNum;i++)

        {

            if(finish[i]==false)

                return false;

        }

        System.out.println("安全序列为:");

        for(int j=0;j<str.length;j++) {

               System.out.print(str[j]);

        }

        System.out.println();

        return true;

    }

    public static void main(String[] args)

    {

        Banker bank = new Banker();

        bank.init();

        System.out.println("===资源分配表===");

        bank.showData();


        int request[] =new int[bank.resNum];

        int requestNum;


        String source[] = new String[bank.resNum];

        for(int i=0;i<bank.resNum;i++) {

               source[i]=((char)('A'+i))+"";

        }

        Scanner s = new Scanner(System.in);

        String choice = new String();


        while(true)

        {

            System.out.println("请输入要请求的进程号（P0--P"+(bank.proNum-1)+"）：");

            requestNum = s.nextInt();

            System.out.println("请输入请求的资源数目");

            for(int i = 0;i<bank.resNum;i++)

            {

                System.out.print("请求"+source[i]+"资源的数目：");

                request[i] = s.nextInt();

            }

            bank.change(requestNum, request);

            System.out.println("提示：是否再请求分配(y/n)");

            choice = s.next();

            if(choice.equals("n")) {

                   System.out.println("提示：谢谢使用，再见!");

                break;

            }  

        }

        s.close();

        bank.sc.close();

    }

  }

（2）init()初始化信息效果图