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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