java 全局变量线程共享吗 java多线程全局变量

import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class PC {

	private static final Lock lock = new ReentrantLock();
	private static final Condition empty = lock.newCondition();
	private static final Condition full = lock.newCondition();
	private static final List<Integer> list = new LinkedList<>();
	private static int size = 0;
	private static int maxSize = 5;
	private static int product = 1;

	public static void put() {
		lock.lock();
		try {
			while (size == maxSize) {
				empty.await();
			}
			list.add(product);
			size++;
			System.out.println("put " + product);
			product++;
			full.signal();
		} catch (InterruptedException e) {
			e.printStackTrace();
		} finally {
			lock.unlock();
		}
	}

	public static void take() {
		lock.lock();
		try {
			while (size == 0) {
				full.await();
			}
			int tep = list.remove(0);
			size--;
			System.out.println("take " + tep);
			empty.signal();
		} catch (InterruptedException e) {
			e.printStackTrace();
		} finally {
			lock.unlock();
		}
	}

	class Producer implements Runnable {
		@Override
		public void run() {
			for (int i = 1; i < 10; i++) {
				put();
				try {
					Thread.sleep(100);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}
	}

	class Consumer implements Runnable {
		@Override
		public void run() {
			for (int i = 1; i < 10; i++) {
				take();
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}
	}

	public static void main(String[] args) {
		PC pc = new PC();
		new Thread(pc.new Producer()).start();
		new Thread(pc.new Consumer()).start();

		new Thread(pc.new Producer()).start();
		new Thread(pc.new Consumer()).start();

	}

}

 

put 1
take 1
put 2
take 2
put 3
put 4
put 5
put 6
put 7
take 3
take 4
put 8
put 9
take 5
take 6
put 10
put 11
take 7
take 8
put 12
put 13
take 9
take 10
put 14
put 15
take 11
take 12
put 16
put 17
take 13
take 14
put 18
take 15
take 16
take 17
take 18