線程的一生
有哪六種狀態?
- New
- Runnable
- Blocked
- Waiting
- Timed Waiting
- Terminated
每個狀態是什麼含義?
新建New、可運行Runnable、已終止Terminated
代碼演示
:
/**
* 展示線程的NEW、RUNNABLE、Terminated狀態。即使是正在運行,也是Runnable狀態,而不是Running。
*/
public class NewRunnableTerminated implements Runnable {
public static void main(String[] args) {
Thread thread = new Thread(new NewRunnableTerminated());
//打印出NEW的狀態
System.out.println(thread.getState());
thread.start();
System.out.println(thread.getState());
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
//打印出RUNNABLE的狀態,即使是正在運行,也是RUNNABLE,而不是RUNNING
System.out.println(thread.getState());
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
//打印出TERMINATED狀態
System.out.println(thread.getState());
}
@Override
public void run() {
for (int i = 0; i < 1000; i++) {
System.out.println(i);
}
}
}
被阻塞Blocked、等待Waiting、計時等待Timed Waiting
代碼演示
:
/**
* 展示Blocked, Waiting, TimedWaiting
*/
public class BlockedWaitingTimedWaiting implements Runnable {
public static void main(String[] args) {
BlockedWaitingTimedWaiting runnable = new BlockedWaitingTimedWaiting();
Thread thread1 = new Thread(runnable);
thread1.start();
Thread thread2 = new Thread(runnable);
thread2.start();
try {
Thread.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
//打印出Timed_Waiting狀態,因爲正在執行Thread.sleep(1000);
System.out.println(thread1.getState());
//打印出BLOCKED狀態,因爲thread2想拿得到sync()的鎖卻拿不到
System.out.println(thread2.getState());
try {
Thread.sleep(1300);
} catch (InterruptedException e) {
e.printStackTrace();
}
//打印出WAITING狀態,因爲執行了wait()
System.out.println(thread1.getState());
}
@Override
public void run() {
syn();
}
private synchronized void syn() {
try {
Thread.sleep(1000);
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
狀態間的轉化圖示
阻塞狀態是什麼?
- 一般來說,把Blocked(被阻塞)、Waiting(等待)、Timed_waiting(計時等待)都稱爲阻塞狀態
- 不僅僅是Blocked
面試問題
1.線程有哪幾種狀態?生命週期是什麼?
先講上面狀態間的轉化圖示圓圈中的狀態名,再講講轉換路徑(例如New只能跳轉到Runnable),最後講講轉移條件。