（一）線程管理_2---獲取和設置線程信息

獲取和設置線程信息

線程中包含一些屬性

ID:線程ID

Name: 

Prioity: 優先級，能夠設置1到10 ，優先級由低到高；

status:線程狀態，共有六個：new, runnable,blocked, waiting, time waiting, terminated

動手實現

public class Calculator implements Runnable {
    private int number;

    public Calculator(int number) {
        this.number = number;
    }

    @Override
    public void run() {
        for (int i = 0; i < number; i++) {
            System.out.printf("%s: %d\n", Thread.currentThread().getName(), i * number);
        }
    }

    public static void main(String[] args) {
        Thread threads[] = new Thread[10];
        Thread.State status[] = new Thread.State[10];

        for (int i = 0; i < 10; i++) {
            threads[i] = new Thread(new Calculator(i));
            if ((i % 2) == 0) {
                threads[i].setPriority(Thread.MAX_PRIORITY);
            } else {
                threads[i].setPriority(Thread.MIN_PRIORITY);
            }
            threads[i].setName("Thread_" + i);
        }

        //將線程狀態變化寫入到文件
        try (FileWriter fileWriter = new FileWriter("thread.log");
             PrintWriter writer = new PrintWriter(fileWriter)) {
            for (int i = 0; i < 10; i++) {
                writer.println("Main : Status of Thread " + i + " : " + threads[i].getState());
                status[i] = threads[i].getState();
            }

            for (int i = 0; i < 10; i++) {
                threads[i].start();
            }

            boolean finish = false;
            while (!finish) {
                for (int i = 0; i < 10; i++) {
                    if (threads[i].getState() != status[i]) {
                        writeThreadInfo(writer, threads[i], status[i]);
                        status[i] = threads[i].getState();
                    }
                }
                finish = true;
                for (int i = 0; i < 10; i++) {
                    finish = finish && (threads[i].getState() == Thread.State.TERMINATED);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static void writeThreadInfo(PrintWriter pw, Thread thread, Thread.State state) {
        pw.printf("Main : Id %d - %s\n", thread.getId(), thread.getName());
        pw.printf("Main : Priority: %d\n", thread.getPriority());
        pw.printf("Main : Old State: %s\n", state);
        pw.printf("Main : New State: %s\n", thread.getState());
        pw.printf("Main : ************************************\n");
    }
}

要點

當沒有指定線程名稱的時候，JVM自動爲線程命名Thread-N （N爲數字）；

如果使用setPriority()設置的優先級參數不合法，將會拋出IllegalArgumentException異常，正常值在1-10之間