NextFitFixedMemory.java

/**
* This is an implementation of Next Fit Memory Allocation Algorithm (Fixed Size Memory Blocks) in Java
*
*    Pseudo code for the algorithm is as follows: 
*
*    Initialize a list of memory blocks with fixed sizes.
*    Create a list of free memory blocks initially containing the entire memory.
*    Initialize a variable j to 0 representing the index of the last allocated memory block.
*    When a new process requests memory allocation:
*        a. Iterate through the list of free memory blocks starting from the last allocated index j.
*        b. If a free memory block is found with a size greater than or equal to the requested size:
*            i. Allocate the memory block to the process.
*            ii. Update the size of the memory block to reflect the allocated size.
*            iii. Remove the allocated memory block from the list of free memory blocks.
*            iv. Set j to the index of the allocated memory block.
*            v. Return the starting address of the allocated memory block to the process.
*        c. If no suitable free memory block is found starting from index j, wrap around to the beginning of the list and continue the search until the last allocated index j is reached again.
*    If no suitable free memory block is found:
*        Indicate that memory allocation failed.
*/

import java.util.Scanner;

public class NextFitFixedMemory {

    public static void nextFitFixedMemory() {
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter number of processes: ");
        int p = scanner.nextInt();
        System.out.print("Enter number of memory blocks: ");
        int n = scanner.nextInt();

        int[] process = new int[p];
        int[] memory = new int[n];

        int[] memoryNextFit = new int[n];

        for (int i = 0; i < n; i++) {
            System.out.print("Enter input for memory block #" + (i + 1) + ": ");
            memory[i] = scanner.nextInt();
        }

        for (int i = 0; i < p; i++) {
            System.out.print("Memory required for process #" + (i + 1) + ": ");
            process[i] = scanner.nextInt();
        }

        System.arraycopy(memory, 0, memoryNextFit, 0, n);

        int[] outputNextFit = new int[p];
        for (int i = 0; i < p; i++) {
            outputNextFit[i] = -1; // Initialize to -1 indicating memory not allocated
        }
        int j = 0; // Start with the first memory block

        for (int i = 0; i < p; i++) {
            while (true) {
                if (process[i] <= memoryNextFit[j]) {
                    outputNextFit[i] = memoryNextFit[j];
                    memoryNextFit[j] = -1;
                    j = (j + 1) % n; // Move to the next memory block
                    break;
                }
                j = (j + 1) % n;
            }
        }

        System.out.println();
        System.out.println("Process No.\tMemory Block Allocated in Next Fit");
        for (int i = 0; i < p; i++) {
            System.out.print((i + 1) + "\t\t\t");
            if (outputNextFit[i] == -1) {
                System.out.print("Memory not allocated\t");
            } else {
                System.out.print(outputNextFit[i] + "\t\t\t");
            }
            System.out.println();
        }

        scanner.close();
    }

    public static void main(String[] args) {
        nextFitFixedMemory();
    }
}