最适合的边界检查的地方 - 构造函数或setter？ [英] Most appropriate place for bounds checking - constructor or setter?

问题描述

还是比较新的Java和我想知道是更好的方式来处理这个。我有一个类构造函数，它接受几个参数，在这个类中还有public getters和setter：

Still relatively new to Java and I'm wondering which is the better way to handle this. I have a class constructor that takes a few parameters, and also in this class are public getters and setters:

private String name;
private Float value;

public MySampleClass(String theName, Float theValue) {
    setName(theName);
    setValue(theValue);
}

public void setName(String n) {
    this.name = n;
}

public value setValue(Float v) {
    this.value = v;
}

我想对这个Float做一些边界检查。它似乎是最好的地方，它将在安装程序：

I'd like to do some bounds checking on this Float. It seems like the best place to put it would be in the setter:

public value setValue(Float v) {
    if (v < 0.0f) {
        this.value = 0.0f;
    } else if (v > 1.0f) {
        this.value = 1.0f;
    }
}

此代码最初在构造函数中检查了边界，再次在安装者，这似乎多余。我改变了构造函数来调用setter并把check放在那里。这是更有意义吗？

This code originally had the bounds checking in the constructor and again in the setter, which seemed redundant. I changed the constructor to call the setter and put the checks in there. Does that make more sense? Or am I violating some convention of which I am completely unaware?

推荐答案

从构造函数调用可覆盖的方法是一个坏主意。做更像这样的事情：

Calling overridable methods from your constructor is a bad idea. Do something more like this:

private String name;
private Float value;

public MySampleClass(String theName, Float theValue) {
    this.name = theName;
    setValueImpl(theValue);
}

public void setName(String n) {
    this.name = n;
}

public void setValue(Float v) {
    setValueImpl(v);
}

private void setValueImpl(Float v) {
    if (v < 0.0f) {
        this.value = 0.0f;
    } else if (v > 1.0f) {
        this.value = 1.0f;
    }
}

这样可以在两个地方验证，调用overridable方法。有关详情，请参见此问题。

This gives you the validation in both places and eliminates the calls to overridable methods. See this question for more on this.

编辑：如果您打算对子类化 MySampleClass 并希望验证设置器可用，请声明 protected final 而不是 private 。

If you plan on subclassing MySampleClass and want the validation setter available, declare it protected final instead of private.

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