我创建的类可以进行自动装箱吗？ [英] Is autoboxing possible for the classes I create?

问题描述

有没有办法为我创建的类使用自动装箱？例如，我有 Number 的子类。

  public class UnsignedInteger扩展数字{
 int n; 
 
 public UnsignedInteger（int n）{
 if（n> = 0）
 this.n = n; 
 else 
抛出新的IllegalArgumentException（仅支持正整数）; 
} 
} 
  

现在， UnsignedInteger i =新的UnsignedInteger（88）; 工作得很好，但有没有办法进行编译： UnsignedInteger i = 88; ？它不适合我。提前致谢！

解决方案

简而言之，没有。没有办法让它编译。<​​/ p>

Java只定义了一组有限的预定义拳击转换。

来自 JLS，部分5.1.7 ：

拳击转换将基本类型的表达式转换为引用类型的相应表达式。具体来说，以下九个转换称为装箱转换：

• 从类型布尔值到类型布尔




• 从类型字节到类型字节




• 从短类型到短类型




• 从char类型到类型Character




• 从int类型到Integer类型




• 从类型long到类型Long




• 从类型float到类型Float




• 从double类型到double类型




• 从null类型到null类型

此外，有人可能会考虑重载 = 运算符来执行此转换，但是在Java中不支持运算符重载，这与C ++不同，这是可能的。

所以你的转换不可能用Java。

Is there any way to use autoboxing for the classes I create? For example, I have this subclass of Number.

public class UnsignedInteger extends Number {
    int n;

    public UnsignedInteger(int n) {
        if(n >= 0)
            this.n = n;
        else
            throw new IllegalArgumentException("Only positive integers are supported");
    }
}

Now, UnsignedInteger i = new UnsignedInteger(88); works perfectly fine, but is there any way to make this compile : UnsignedInteger i = 88;? It won't for me. Thanks in advance!

解决方案

In short, no. There's no way to get that to compile.

Java only defines a limited set of pre-defined boxing conversions.

From the JLS, section 5.1.7:

Boxing conversion converts expressions of primitive type to corresponding expressions of reference type. Specifically, the following nine conversions are called the boxing conversions:

• From type boolean to type Boolean

• From type byte to type Byte

• From type short to type Short

• From type char to type Character

• From type int to type Integer

• From type long to type Long

• From type float to type Float

• From type double to type Double

• From the null type to the null type

Additionally, one might think of overloading the = operator to perform this conversion, but operator overloading is not supported in Java, unlike in C++, where this would be possible.

So your conversion is not possible in Java.

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