Java：Enum vs. Int [英] Java: Enum vs. Int

问题描述

在Java中使用标志时，我已经看到两种主要方法。一个使用int值和一行if-else语句。另一个是使用枚举和case-switch语句。

When using flags in Java, I have seen two main approaches. One uses int values and a line of if-else statements. The other is to use enums and case-switch statements.

我想知道在使用枚举与int之间的内存使用率和速度方面是否有差异？

I was wondering if there was a difference in terms of memory usage and speed between using enums vs ints for flags?

推荐答案

ints 和 code>可以同时使用switch或if-then-else，内存使用量对于两者来说也是最小的，速度是相似的 - 它们之间没有显着差异。

Both ints and enums can use both switch or if-then-else, and memory usage is also minimal for both, and speed is similar - there's no significant difference between them on the points you raised.

但是，最重要的区别是类型检查。 枚举被检查， ints 不是。

However, the most important difference is the type checking. Enums are checked, ints are not.

这个代码：

public class SomeClass {
    public static int RED = 1;
    public static int BLUE = 2;
    public static int YELLOW = 3;
    public static int GREEN = 3; // sic

    private int color;

    public void setColor(int color) {
        this.color = color;
    }   
}

虽然许多客户端将正确使用这个， >

While many clients will use this properly,

new SomeClass().setColor(SomeClass.RED);

没有任何东西阻止他们写这个：

There is nothing stopping them from writing this:

new SomeClass().setColor(999);

使用 public static final pattern：

There are three main problems with using the public static final pattern:

• 问题发生在运行时，而不是编译 ，所以修复更昂贵，更难找到原因


• 你必须编写代码来处理不好的输入 - 通常是一个 if-then-否则与最终 else throw new IllegalArgumentException（未知颜色+颜色）; - 再次昂贵


• 没有什么可以防止常量的冲突 - 即使 YELLOW 和 GREEN 都可以编译上述类代码，相同的值 3

• The problem occurs at runtime, not compile time, so it's going to be more expensive to fix, and harder to find the cause
• You have to write code to handle bad input - typically a if-then-else with a final else throw new IllegalArgumentException("Unknown color " + color); - again expensive
• There is nothing preventing a collision of constants - the above class code will compile even though YELLOW and GREEN both have the same value 3

如果您使用枚举，您解决所有这些问题：

If you use enums, you address all these problems:

• 您的代码将无法编译，除非您在


• 不需要任何特殊的错误输入代码 - 编译器为您处理


• 枚举值为un ique

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