--------- beginning of system 和 --------- beginning of main 区别

"--------- beginning of system" 和 "--------- beginning of main" 是在代码文件中的两个标记，用于区分系统代码和主要代码的不同部分。

"--------- beginning of system" 标记通常用于指示系统级别的代码，例如导入库、全局变量的定义、配置设置等。这部分代码是整个程序的基础，用于提供必要的功能和资源。

而 "--------- beginning of main" 标记通常用于指示主要的业务逻辑代码，例如函数的定义、程序的入口点等。这部分代码是程序的核心，用于执行实际的任务和操作。

通过使用这样的标记，开发人员可以更清晰地区分系统级别代码和主要代码，使代码结构更加清晰和易于维护。

相关问题

130|console:/ # logcat -s alogd --------- beginning of kernel --------- beginning of system --------- beginning of main

根据提供的引用内容，您想了解如何使用logcat命令查看Android设备的日志。logcat命令用于查看系统日志和应用程序日志。以下是使用logcat命令查看Android设备日志的示例：

logcat -s alogd

这个命令将过滤并显示与"alogd"相关的日志信息。请注意，您需要在Android设备上运行此命令，并且您的设备必须具有root权限才能访问系统日志。

用java语言实现实现银行家算法、进程调度过程的模拟、读者-写者问题的写者优先算法。

银行家算法的Java实现：

import java.util.Scanner;

public class BankersAlgorithm {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter the number of processes: ");
        int n = sc.nextInt();

        System.out.print("Enter the number of resources: ");
        int m = sc.nextInt();

        int[][] max = new int[n][m];
        int[][] allocation = new int[n][m];
        int[][] need = new int[n][m];
        int[] available = new int[m];

        System.out.println("Enter the maximum matrix:");
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                max[i][j] = sc.nextInt();
            }
        }

        System.out.println("Enter the allocation matrix:");
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                allocation[i][j] = sc.nextInt();
            }
        }

        System.out.println("Enter the available matrix:");
        for (int i = 0; i < m; i++) {
            available[i] = sc.nextInt();
        }

        // Calculate the need matrix
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                need[i][j] = max[i][j] - allocation[i][j];
            }
        }

        // Check if the system is in a safe state
        if (isSafe(n, m, allocation, need, available)) {
            System.out.println("The system is in a safe state.");
        } else {
            System.out.println("The system is not in a safe state.");
        }
    }

    public static boolean isSafe(int n, int m, int[][] allocation, int[][] need, int[] available) {
        boolean[] visited = new boolean[n];
        int[] work = new int[m];

        // Initialize the work matrix
        for (int i = 0; i < m; i++) {
            work[i] = available[i];
        }

        // Initialize the visited matrix
        for (int i = 0; i < n; i++) {
            visited[i] = false;
        }

        // Find an unvisited process that can be completed
        for (int i = 0; i < n; i++) {
            if (!visited[i] && canComplete(i, m, allocation, need, work)) {
                visited[i] = true;

                // Add the allocated resources to the work matrix
                for (int j = 0; j < m; j++) {
                    work[j] += allocation[i][j];
                }

                // Start over from the beginning of the process list
                i = -1;
            }
        }

        // Check if all processes have been visited
        for (int i = 0; i < n; i++) {
            if (!visited[i]) {
                return false;
            }
        }

        return true;
    }

    public static boolean canComplete(int i, int m, int[][] allocation, int[][] need, int[] work) {
        for (int j = 0; j < m; j++) {
            if (need[i][j] > work[j]) {
                return false;
            }
        }

        return true;
    }
}

进程调度过程的模拟的Java实现：

import java.util.Arrays;
import java.util.Scanner;

public class ProcessScheduling {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter the number of processes: ");
        int n = sc.nextInt();

        int[] arrivalTime = new int[n];
        int[] burstTime = new int[n];
        int[] completionTime = new int[n];
        int[] waitingTime = new int[n];
        int[] turnaroundTime = new int[n];
        int[] remainingTime = new int[n];

        for (int i = 0; i < n; i++) {
            System.out.print("Enter the arrival time of process " + (i + 1) + ": ");
            arrivalTime[i] = sc.nextInt();

            System.out.print("Enter the burst time of process " + (i + 1) + ": ");
            burstTime[i] = sc.nextInt();

            remainingTime[i] = burstTime[i];
        }

        // Sort the processes by arrival time
        sortProcesses(n, arrivalTime, burstTime);

        int time = 0;
        int completed = 0;

        while (completed < n) {
            int i = getNextProcess(n, arrivalTime, remainingTime, time);

            if (i == -1) {
                time++;
            } else {
                remainingTime[i]--;

                if (remainingTime[i] == 0) {
                    completionTime[i] = time + 1;
                    waitingTime[i] = completionTime[i] - arrivalTime[i] - burstTime[i];
                    turnaroundTime[i] = completionTime[i] - arrivalTime[i];
                    completed++;
                }

                time++;
            }
        }

        double avgWaitingTime = getAverage(waitingTime);
        double avgTurnaroundTime = getAverage(turnaroundTime);

        System.out.println("Process\tArrival Time\tBurst Time\tCompletion Time\tWaiting Time\tTurnaround Time");
        for (int i = 0; i < n; i++) {
            System.out.println((i + 1) + "\t\t" + arrivalTime[i] + "\t\t" + burstTime[i] + "\t\t" + completionTime[i] + "\t\t" + waitingTime[i] + "\t\t" + turnaroundTime[i]);
        }
        System.out.println("Average waiting time: " + avgWaitingTime);
        System.out.println("Average turnaround time: " + avgTurnaroundTime);
    }

    public static void sortProcesses(int n, int[] arrivalTime, int[] burstTime) {
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                if (arrivalTime[i] > arrivalTime[j]) {
                    swap(arrivalTime, i, j);
                    swap(burstTime, i, j);
                }
            }
        }
    }

    public static int getNextProcess(int n, int[] arrivalTime, int[] remainingTime, int time) {
        int minRemainingTime = Integer.MAX_VALUE;
        int nextProcess = -1;

        for (int i = 0; i < n; i++) {
            if (arrivalTime[i] <= time && remainingTime[i] > 0 && remainingTime[i] < minRemainingTime) {
                minRemainingTime = remainingTime[i];
                nextProcess = i;
            }
        }

        return nextProcess;
    }

    public static double getAverage(int[] arr) {
        double sum = 0;

        for (int i = 0; i < arr.length; i++) {
            sum += arr[i];
        }

        return sum / arr.length;
    }

    public static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
}

读者-写者问题的写者优先算法的Java实现：

import java.util.concurrent.Semaphore;

public class ReaderWriter {

    private static int readCount = 0;
    private static Semaphore rMutex = new Semaphore(1);
    private static Semaphore wMutex = new Semaphore(1);
    private static Semaphore resource = new Semaphore(1);

    public static void main(String[] args) {
        Thread[] readers = new Thread[3];
        Thread[] writers = new Thread[2];

        for (int i = 0; i < readers.length; i++) {
            readers[i] = new Thread(new Reader(i));
            readers[i].start();
        }

        for (int i = 0; i < writers.length; i++) {
            writers[i] = new Thread(new Writer(i));
            writers[i].start();
        }
    }

    static class Reader implements Runnable {
        private int id;

        public Reader(int id) {
            this.id = id;
        }

        public void run() {
            while (true) {
                try {
                    // Acquire the rMutex semaphore to ensure mutual exclusion
                    rMutex.acquire();

                    // Increment the read count
                    readCount++;

                    // If this is the first reader, acquire the resource semaphore to prevent writers from accessing the resource
                    if (readCount == 1) {
                        resource.acquire();
                    }

                    // Release the rMutex semaphore to allow other readers to access the read count
                    rMutex.release();

                    // Read the resource
                    System.out.println("Reader " + id + " is reading the resource.");

                    // Acquire the rMutex semaphore to ensure mutual exclusion
                    rMutex.acquire();

                    // Decrement the read count
                    readCount--;

                    // If this is the last reader, release the resource semaphore to allow writers to access the resource
                    if (readCount == 0) {
                        resource.release();
                    }

                    // Release the rMutex semaphore to allow other readers to access the read count
                    rMutex.release();

                    // Sleep for a random amount of time
                    Thread.sleep((long)(Math.random() * 100));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    static class Writer implements Runnable {
        private int id;

        public Writer(int id) {
            this.id = id;
        }

        public void run() {
            while (true) {
                try {
                    // Acquire the wMutex semaphore to ensure mutual exclusion
                    wMutex.acquire();

                    // Acquire the resource semaphore to prevent other writers and readers from accessing the resource
                    resource.acquire();

                    // Write to the resource
                    System.out.println("Writer " + id + " is writing to the resource.");

                    // Release the resource semaphore to allow other writers and readers to access the resource
                    resource.release();

                    // Release the wMutex semaphore to allow other writers to access the resource
                    wMutex.release();

                    // Sleep for a random amount of time
                    Thread.sleep((long)(Math.random() * 100));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}