callable | 易学教程

How to ensure garbage collection of a FutureTask that is submitted to a ThreadPoolExecutor and then cancelled?

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问题 I am submitting Callable objects to a ThreadPoolExecutor and they seem to be sticking around in memory. Looking at the heap dump with the MAT tool for Eclipse see that the Callable objects are being referenced by a FutureTask$Sync 's callable variable. That FutureTask$Sync is referenced by a FutureTask 's sync variable. That FutureTask is referenced by the FutureTask$Sync 's this$0 variable. I have read around about this (here, here, and on SO) and it seems like the FutureTask that the

What's the difference between Future and FutureTask in Java?

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Since use ExecutorService can submit a Callable task and return a Future , why need to use FutureTask to wrap Callable task and use the method execute ? I feel they both do the same thing. In fact you are correct. The two approaches are identical. You generally don't need to wrap them yourself. If you are, you're likely duplicating the code in AbstractExecutorService: /** * Returns a <tt>RunnableFuture</tt> for the given callable task. * * @param callable the callable task being wrapped * @return a <tt>RunnableFuture</tt> which when run will call the * underlying callable and which, as a <tt

How to return object from Callable()

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I'm trying to return a 2d array from call(), I'm having some issues. My code so far is: //this is the end of main Thread t1 = new Thread(new ArrayMultiplication(Array1, Array2, length)); t1.start(); } public int[][] call(int[][] answer) { int[][] answer = new int[length][length]; answer = multiplyArray(Array1, Array2, length); //off to another function which returns the answer to here return answer; } This code compiles, this is not returning my array. I'm sure I'm probably using the wrong syntax, but I can't find any good examples. EDIT: changed it a bit Adding to Joseph Ottinger's answer, to

How can I terminate Tasks that have timed out in multithreading?

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问题 I need to make a library in which I will have synchronous and asynchronous methods in it. executeSynchronous() - waits until I have a result, returns the result. executeAsynchronous() - returns a Future immediately which can be processed after other things are done, if needed. Core Logic of my Library The customer will use our library and they will call it by passing DataKey builder object. We will then construct a URL by using that DataKey object and make a HTTP client call to that URL by

How to pass a parameter to Scikit-Learn Keras model function

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I have the following code, using Keras Scikit-Learn Wrapper , which work fine: from keras.models import Sequential from keras.layers import Dense from sklearn import datasets from keras.wrappers.scikit_learn import KerasClassifier from sklearn.model_selection import StratifiedKFold from sklearn.model_selection import cross_val_score import numpy as np def create_model(): # create model model = Sequential() model.add(Dense(12, input_dim=4, init='uniform', activation='relu')) model.add(Dense(6, init='uniform', activation='relu')) model.add(Dense(1, init='uniform', activation='sigmoid')) #

“TypeError: native Qt signal is not callable” with custom slots

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问题 The Environment I am running an Anaconda environment with Python 3.4. I am using PyCharm as my IDE. The Objective I am trying to make a pyQt4 QPushButton connect to a custom function: button.clicked().connect([method reference or whatever]) Attempts I have tried using the pyqtSlot() decorator but when I run the code it throws: NameError: name 'pyqtSlot' is not defined I have used the following imports which should include that decorator: from PyQt4 import QtCore, QtGui I also attempted to

Basic method chaining

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问题 I found this method chaining in python, but even with it I couldn't understand method chaining in Python. Here the goals are two: solve the coding problem and understand method chaining (given that I am still not 100% confident with callables). Down to the problem definition. I want a class that has two methods: one sets a parameter of the object = 'line' and the other overwrites to 'bar'. This is what I got so far: class foo(): def __init__(self, kind=None): self.kind = kind def __call__

Why do we have callable objects in python?

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问题 What is the purpose of a callable object? What problems do they solve? 回答1: They take parameters and return a result depending on those parameters. A callable is just an abstract form of a function resp an interface that defines that an object acts like a function (i.e. accepts parameters). As functions are first class objects, it is obvious that functions are callable objects. If you are talking about the __call__ method, this is just one of the many special methods with which you can

What's the difference between Future and FutureTask in Java?

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问题 Since use ExecutorService can submit a Callable task and return a Future , why need to use FutureTask to wrap Callable task and use the method execute ? I feel they both do the same thing. 回答1: In fact you are correct. The two approaches are identical. You generally don't need to wrap them yourself. If you are, you're likely duplicating the code in AbstractExecutorService: /** * Returns a <tt>RunnableFuture</tt> for the given callable task. * * @param callable the callable task being wrapped

Odd method call in java using a dot operator to access a generic list

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I came across some advanced java code (advanced for me :) ) I need help understanding. In a class there is a nested class as below: private final class CoverageCRUDaoCallable implements Callable<List<ClientCoverageCRU>> { private final long oid; private final long sourceContextId; private CoverageCRUDaoCallable(long oid, long sourceContextId) { this.oid = oid; this.sourceContextId = sourceContextId; } @Override public List<ClientCoverageCRU> call() throws Exception { return coverageCRUDao.getCoverageCRUData(oid, sourceContextId); } } Later in the outer class, there is an instance of the