英文:
Block actions till list becomes non-empty with java.util.concurrent
问题
我需要你的帮助。我应该在我的练习中使用java.util.concurrent包，但我不知道该如何做。问题仅涉及get方法。
如何编写代码以等待给定的列表（变量：inputList）变为非空？
问候
英文:
I need your help. I should use the java.util.concurrent package in my exercise but I don't know how to do it. The question is only about the get method.
public String getInput() {if (inputList.isEmpty()) return null;String input = inputList.get(0);inputList.remove(0);return input;}
How do I need to write the code to wait till the given list (variable: inputList) becomes non-empty?
Greetings
答案1
得分: 0
you could try using the LinkedBlockingDeque class from the java.util.concurrent
package which implements the BlockingDequeinterface.
it lets you add items to the BlockingDeque and the take* methods block until there is an element available and remove it after fetching. Have a look at the Javadoc
Here is an example:
public class Queue {BlockingDeque<String> inputList = new LinkedBlockingDeque<>();public String getInput() {try {System.out.println("waiting on queue");String input = inputList.takeFirst();System.out.println("taken " + input);return input;} catch (InterruptedException e) {e.printStackTrace();return null;}}public static void main(String[] args) {Queue queue = new Queue();new Thread(() -> {try {Thread.sleep(4000);queue.inputList.add("string");System.out.println("added string");Thread.sleep(2000);queue.inputList.add("string1");System.out.println("added string 1");} catch (InterruptedException e) {e.printStackTrace();}}).start();for (int i = 0; i < 2; i++){queue.getInput();}}}
英文:
you could try using the LinkedBlockingDeque class from the java.util.concurrent
package which implements the BlockingDequeinterface.
it lets you add items to the BlockingDeque and the take* methods block until there is an element available and remove it after fetching. Have a look at the Javadoc
Here is an example:
public class Queue {BlockingDeque<String> inputList = new LinkedBlockingDeque<>();public String getInput() {try {System.out.println("waiting on queue");String input = inputList.takeFirst();System.out.println("taken " + input);return input;} catch (InterruptedException e) {e.printStackTrace();return null;}}public static void main(String[] args) {Queue queue = new Queue();new Thread(() -> {try {Thread.sleep(4000);queue.inputList.add("string");System.out.println("added string");Thread.sleep(2000);queue.inputList.add("string1");System.out.println("added string 1");} catch (InterruptedException e) {e.printStackTrace();}}).start();for (int i = 0; i < 2; i++){queue.getInput();}}}
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