问题
I have multiple arrays whose sizes need to be determined by the user input. These arrays should be accessible in the main method as well as the stepTwo() method. However, I am stuck. The user input doesn't come until the main method, but if I declare the arrays in the main method, then I can't access the arrays in the stepTwo() method. I would prefer not to pass the arrays as parameters to stepTwo() as I tried that before but came up with multiple errors. Any suggestions? See below for complete code:
public class AssignmentIII
{
public static int numProcesses; // Represents the number of processes
public static int numResources; // Represents the number of different types of resources
public static int[] available = new int[numResources]; // Create an emptry matrix for available processes
public static int[][] allocation = new int[numProcesses][numResources]; // Create an empty allocation matrix nxm
public static int[][] request = new int[numProcesses][numResources]; // Create an empty request matrix nxm
public static int[] work = new int[numResources]; // Create an empty work matrix
public static Boolean[] finish = new Boolean[numProcesses]; // Create an empty finish matrix
public static void main(String[] args) throws FileNotFoundException
{
try
{
Scanner scan = new Scanner(System.in);
Scanner fileScan = new Scanner(new File("input1.txt")); // Create file scanner
System.out.println("Please enter the total number of processes: ");
numProcesses = scan.nextInt();
System.out.println("Please enter the number of different types of resources: ");
numResources = scan.nextInt();
// Initialize the available matrix
for(int i = 0; i < numResources; i++)
available[i]=fileScan.nextInt();
// Initialize the allocation matrix
for(int j = 0; j < numProcesses; j++)
for(int k = 0; k < numResources; k++)
allocation[j][k]=fileScan.nextInt();
// Initialize the request matrix
for(int m = 0; m < numProcesses; m++)
for(int n = 0; n < numResources; n++)
request[m][n]=fileScan.nextInt();
// Print allocation matrix
System.out.println();
System.out.println("Allocated");
for(int i = 0; i < numResources; i++)
{
System.out.print("\tR" + i);
}
System.out.println();
for(int j = 0; j < numProcesses; j++)
{
System.out.print("P" + j);
for(int k = 0; k < numResources; k++)
{
System.out.print("\t" + allocation[j][k]);
}
System.out.println();
}
// Print available matrix
System.out.println();
System.out.println("Available");
for(int i = 0; i < numResources; i++)
{
System.out.print("R" + i + "\t");
}
System.out.println();
for(int i = 0; i < numResources; i++)
System.out.print(available[i] + "\t");
System.out.println();
// Print request matrix
System.out.println();
System.out.println("Requested");
for(int i = 0; i < numResources; i++)
{
System.out.print("\tR" + i);
}
System.out.println();
for(int m = 0; m < numProcesses; m++)
{
System.out.print("P" + m);
for(int n = 0; n < numResources; n++)
{
System.out.print("\t" + request[m][n]);
}
System.out.println();
}
System.out.println();
// Begin deadlock detection algorithm
for(int i = 0; i < numResources; i++) // Intialize Work := Available
work[i]=available[i];
for(int j = 0; j < numProcesses; j++) // Check for Allocation != 0 and initialize Finish accordingly
{
int sumAllocation = 0;
for(int i = 0; i < numResources; i++)
{
sumAllocation += allocation[j][i];
}
if (sumAllocation != 0)
finish[j] = false;
else finish[j] = true;
}
stepTwo();
}
catch(FileNotFoundException ex)
{
System.out.println("An error has occured. The file cannot be found.");
}
}
public static void stepTwo()
{
// Step 2
// Find an index i where Finish[i] = false & Request[i] <= Work
for(int i = 0; i < numProcesses; i++)
{
int sumRequests = 0;
int sumWork = 0;
// Sum the Request and Work vectors
for(int k = 0; k < numResources; k++)
{
sumRequests += request[i][k];
sumWork += work[k];
}
if (finish[i] == false && sumRequests <= sumWork)
{
finish[i] = true;
for(int m = 0; m < numResources; m++)
{
work[m] = work[m] + allocation[i][m];
}
stepTwo();
}
else if (finish[i] == false)
// Step 4: Print which processes are in a deadlock state
// Print using P0, P1, ... , Pn format
System.out.println("P" + i + " is in a deadlock state.");
}
}
}
回答1:
Declare the array as you do - "above main", but initialize it after reading in the appropriate size.
Declaration:
public static int[] available;
Initialization:
available = new int[numResources];
回答2:
you must initialize the array into de main block, something like this.
public class AssignmentIII
{
public static int numProcesses; // Represents the number of processes
public static int numResources; // Represents the number of different types of resources
public static int[] available ;
public static int[][] allocation ;
public static int[][] request ;
public static int[] work ;
public static Boolean[] finish ;
public static void main(String[] args) throws FileNotFoundException
{
try
{
Scanner scan = new Scanner(System.in);
Scanner fileScan = new Scanner(new File("input1.txt")); // Create file scanner
System.out.println("Please enter the total number of processes: ");
numProcesses = scan.nextInt();
System.out.println("Please enter the number of different types of resources: ");
numResources = scan.nextInt();
available = new int[numResources]; // Create an emptry matrix for available processes
allocation = new int[numProcesses][numResources]; // Create an empty allocation matrix nxm
request = new int[numProcesses][numResources]; // Create an empty request matrix nxm
work = new int[numResources]; // Create an empty work matrix
finish = new Boolean[numProcesses]; // Create an empty finish matrix
// Initialize the available matrix
for(int i = 0; i < numResources; i++)
available[i]=fileScan.nextInt();
// Initialize the allocation matrix
for(int j = 0; j < numProcesses; j++)
for(int k = 0; k < numResources; k++)
allocation[j][k]=fileScan.nextInt();
// Initialize the request matrix
for(int m = 0; m < numProcesses; m++)
for(int n = 0; n < numResources; n++)
request[m][n]=fileScan.nextInt();
// Print allocation matrix
System.out.println();
System.out.println("Allocated");
for(int i = 0; i < numResources; i++)
{
System.out.print("\tR" + i);
}
System.out.println();
for(int j = 0; j < numProcesses; j++)
{
System.out.print("P" + j);
for(int k = 0; k < numResources; k++)
{
System.out.print("\t" + allocation[j][k]);
}
System.out.println();
}
// Print available matrix
System.out.println();
System.out.println("Available");
for(int i = 0; i < numResources; i++)
{
System.out.print("R" + i + "\t");
}
System.out.println();
for(int i = 0; i < numResources; i++)
System.out.print(available[i] + "\t");
System.out.println();
// Print request matrix
System.out.println();
System.out.println("Requested");
for(int i = 0; i < numResources; i++)
{
System.out.print("\tR" + i);
}
System.out.println();
for(int m = 0; m < numProcesses; m++)
{
System.out.print("P" + m);
for(int n = 0; n < numResources; n++)
{
System.out.print("\t" + request[m][n]);
}
System.out.println();
}
System.out.println();
// Begin deadlock detection algorithm
for(int i = 0; i < numResources; i++) // Intialize Work := Available
work[i]=available[i];
for(int j = 0; j < numProcesses; j++) // Check for Allocation != 0 and initialize Finish accordingly
{
int sumAllocation = 0;
for(int i = 0; i < numResources; i++)
{
sumAllocation += allocation[j][i];
}
if (sumAllocation != 0)
finish[j] = false;
else finish[j] = true;
}
stepTwo();
}
catch(FileNotFoundException ex)
{
System.out.println("An error has occured. The file cannot be found.");
}
}
public static void stepTwo()
{
// Step 2
// Find an index i where Finish[i] = false & Request[i] <= Work
for(int i = 0; i < numProcesses; i++)
{
int sumRequests = 0;
int sumWork = 0;
// Sum the Request and Work vectors
for(int k = 0; k < numResources; k++)
{
sumRequests += request[i][k];
sumWork += work[k];
}
if (finish[i] == false && sumRequests <= sumWork)
{
finish[i] = true;
for(int m = 0; m < numResources; m++)
{
work[m] = work[m] + allocation[i][m];
}
stepTwo();
}
else if (finish[i] == false)
// Step 4: Print which processes are in a deadlock state
// Print using P0, P1, ... , Pn format
System.out.println("P" + i + " is in a deadlock state.");
}
}
}
but this, is not a recommended way. Because is not the right way for use the static method and static attribute. Furthermore you should use encapsulation. Using a better design and encapsulation method, your code can be improved something like this.
public class AssignmentIII
{
int numProcesses; // Represents the number of processes
int numResources; // Represents the number of different types of resources
String filepath;
int[] available = new int[numResources]; // Create an emptry matrix for available processes
int[][] allocation = new int[numProcesses][numResources]; // Create an empty allocation matrix nxm
int[][] request = new int[numProcesses][numResources]; // Create an empty request matrix nxm
int[] work = new int[numResources]; // Create an empty work matrix
Boolean[] finish = new Boolean[numProcesses]; // Create an empty finish matrix
public AssignmentIII(int numResources,int numProcesses, String filepath){
this.numProcesses = numProcesses;
this.numResources = numResources;
this.filepath = filepath;
available = new int[numResources]; // Create an emptry matrix for available processes
allocation = new int[numProcesses][numResources]; // Create an empty allocation matrix nxm
request = new int[numProcesses][numResources]; // Create an empty request matrix nxm
work = new int[numResources]; // Create an empty work matrix
finish = new Boolean[numProcesses]; // Create an empty finish matrix
}
public void initilizeMatrix() throws FileNotFoundException{
Scanner fileScan = new Scanner(new File(filepath)); // Create file scanner
// Initialize the available matrix
for(int i = 0; i < numResources; i++)
available[i]=fileScan.nextInt();
// Initialize the allocation matrix
for(int j = 0; j < numProcesses; j++)
for(int k = 0; k < numResources; k++)
allocation[j][k]=fileScan.nextInt();
// Initialize the request matrix
for(int m = 0; m < numProcesses; m++)
for(int n = 0; n < numResources; n++)
request[m][n]=fileScan.nextInt();
fileScan.close();
}
public void print(){
// Print allocation matrix
System.out.println();
System.out.println("Allocated");
for(int i = 0; i < numResources; i++)
{
System.out.print("\tR" + i);
}
System.out.println();
for(int j = 0; j < numProcesses; j++)
{
System.out.print("P" + j);
for(int k = 0; k < numResources; k++)
{
System.out.print("\t" + allocation[j][k]);
}
System.out.println();
}
// Print available matrix
System.out.println();
System.out.println("Available");
for(int i = 0; i < numResources; i++)
{
System.out.print("R" + i + "\t");
}
System.out.println();
for(int i = 0; i < numResources; i++)
System.out.print(available[i] + "\t");
System.out.println();
// Print request matrix
System.out.println();
System.out.println("Requested");
for(int i = 0; i < numResources; i++)
{
System.out.print("\tR" + i);
}
System.out.println();
for(int m = 0; m < numProcesses; m++)
{
System.out.print("P" + m);
for(int n = 0; n < numResources; n++)
{
System.out.print("\t" + request[m][n]);
}
System.out.println();
}
System.out.println();
}
// Begin deadlock detection algorithm
public void deadLockdetecter(){
for(int i = 0; i < numResources; i++) // Intialize Work := Available
work[i]=available[i];
for(int j = 0; j < numProcesses; j++) // Check for Allocation != 0 and initialize Finish accordingly
{
int sumAllocation = 0;
for(int i = 0; i < numResources; i++)
{
sumAllocation += allocation[j][i];
}
if (sumAllocation != 0)
finish[j] = false;
else finish[j] = true;
}
}
public void stepTwo()
{
// Step 2
// Find an index i where Finish[i] = false & Request[i] <= Work
for(int i = 0; i < numProcesses; i++)
{
int sumRequests = 0;
int sumWork = 0;
// Sum the Request and Work vectors
for(int k = 0; k < numResources; k++)
{
sumRequests += request[i][k];
sumWork += work[k];
}
if (finish[i] == false && sumRequests <= sumWork)
{
finish[i] = true;
for(int m = 0; m < numResources; m++)
{
work[m] = work[m] + allocation[i][m];
}
stepTwo();
}
else if (finish[i] == false)
// Step 4: Print which processes are in a deadlock state
// Print using P0, P1, ... , Pn format
System.out.println("P" + i + " is in a deadlock state.");
}
}
public static void main(String[] args) throws FileNotFoundException
{
AssignmentIII assignment;
String p_filepath;
int p_numProcesses;
int p_numResources;
p_filepath = "inpu1t.txt";
Scanner scan = new Scanner(System.in);
System.out.println("Please enter the total number of processes: ");
p_numProcesses = scan.nextInt();
System.out.println("Please enter the number of different types of resources: ");
p_numResources = scan.nextInt();
scan.close();
assignment = new AssignmentIII(p_numResources, p_numProcesses, p_filepath);
try
{
assignment.initilizeMatrix();
}
catch(FileNotFoundException ex)
{
System.out.println("An error has occured. The file cannot be found.");
}
assignment.stepTwo();
}
}
来源：https://stackoverflow.com/questions/29086903/how-to-create-public-array-accessible-by-all-methods-but-have-user-input-determ