JDK中的模板设计模式，找不到定义要执行的方法集的方法 [英] Template design pattern in JDK, could not find a method defining set of methods to be executed in order

问题描述

我正在阅读模板设计模式。根据我目前的理解，当我们有一个具有定义的一组过程（方法）的算法时，可以使用模板设计模式。
主要玩家是

1。抽象模板类提供模板方法定义进程（方法）和执行顺序。通常这种方法是最终的，因为它的行为没有被修改。提供了模板方法中提到的几个进程（方法）默认实现，其他依赖于将抽象模板类类型的具体类放置为抽象。

2。扩展模板方法的具体类。这些覆盖默认方法，如果需要，并提供了抽象模板类中定义的抽象方法的实现。

我尝试在JDK中搜索其实现， code> java.io 类后，看到这些类实现了这个模式。我无法找到定义一组进程（方法）和执行顺序的任何方法。

请提供宝贵的意见。

解决方案

一个简单的例子 java.io.OutputStream 。

模板方法是 public void write（byte b []，int off，int len）。

它调用抽象方法

public abstract void write（int b），
_由 OutputStream 的子类实现。

在这种情况下，模板的不变部分是基本的错误处理对于每个 OutputStream 是常见的，而模板的变体部分是实际的写作，具体是每个具体的实现。

$ b $你对模式的理解是正确的;然而，它不需要那么复杂。基本上，在同一个类中调用抽象方法的任何具体方法都是一种模板方法。

I am reading about Template design pattern. As per my current understanding, Template design pattern can be used when we have an algorithm with defined set of processes(methods) to be done in order. Main players are

1.Abstract Template class providing a template method defining the processes (methods) and the order of execution. Usually this method is made final, so as its behavior is not modified. Few of the processes(methods) mentioned in the template method are provided with default implementation and others depending upon the concrete classes extending the Abstract template class types are left as abstract.

2.Concrete classes extending the Template method. These override the default methods if necessary and provided the implementation for the abstract methods defined in the Abstract Template class.

I tried searching for its implementation in JDK, i looked at java.io classes after reading that these classes implement this pattern. I was not able to find any method defining a set of processes(methods) and the order of execution.

Please provide your valuable inputs.

解决方案

A simple example is java.io.OutputStream.

The template method is
public void write(byte b[], int off, int len).

It calls the abstract method
public abstract void write(int b),
which must be implemented by a subclass of OutputStream.

In this case the invariant portion of the template is the basic error handling that is common to every OutputStream, while the variant portion of the template is the actual writing, which is specific to each concrete implementation.

Your understanding of the pattern is correct; however, it needn't be that complex. Basically, any concrete method which calls an abstract method in the same class is a template method.

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