The question reads:

After client complaints, it is observed that the memory usage of the Worker component constantly increases, even if the memory is supposedly released by the Worker. Fix the issue without changing the public API of TaskResource and Worker.

And the code is:

import java.util.*;
import java.util.HashMap;

public class Worker {
    private HashMap<Integer, TaskResource> taskResources = new HashMap<Integer, TaskResource>();

    public Iterable<TaskResource> getTaskResources() {
        return this.taskResources.values();
    }

    public TaskResource acquireTaskResource(int id) {
        TaskResource w = this.taskResources.getOrDefault(id, null);
        if (w == null) {
            w = new TaskResource(id);
            this.taskResources.put(id, w);
        }

        return w;
    }

    public void releaseTaskResource(int id) {
        TaskResource w = this.taskResources.getOrDefault(id, null);
        if (w == null)
            throw new IllegalArgumentException();

        w.close();
    }

    public class TaskResource implements AutoCloseable {
        private List<String> taskList = new ArrayList<String>();

        private int id;

        public int getId() {
            return this.id;
        }

        public List<String> getTasks() {
            return this.taskList;
        }

        public TaskResource(int id) {
            this.id = id;
        }

        public void doTask(String task) {
            if (this.taskList == null)
                throw new IllegalStateException(this.getClass().getName());

            this.taskList.add(task);
        }

        @Override
        public void close() {
            this.taskList = null;
        }
    }

    public static void main(String[] args) {
        Worker d = new Worker();

        d.acquireTaskResource(1).doTask("Task11");
        d.acquireTaskResource(2).doTask("Task21");
        System.out.println(String.join(", ", d.acquireTaskResource(2).getTasks()));
        d.releaseTaskResource(2);
        d.acquireTaskResource(1).doTask("Task12");
        System.out.println(String.join(", ", d.acquireTaskResource(1).getTasks()));
        d.releaseTaskResource(1);
    }
}

I'm not really sure where to begin. I don't even understand what the purpose of code like this would even be. Can I get a nudge in the right direction?

CodePudding user response：

Currently, when you release a task resource you do not remove the associated Task from the taskResources HashMap. Thus it will grow forever. Add a line of code to remove it from the Map. Like,

public void releaseTaskResource(int id) {
    TaskResource w = this.taskResources.getOrDefault(id, null);
    if (w == null) {
        throw new IllegalArgumentException();
    }
    w.close();
    this.taskResources.remove(id);
}