将float转换为int [英] Converting float to int

问题描述

我来自Python背景并深入研究Java世界。
我试图在Java中将Float转换为int。我们在Python中做的事情 int_var = int（float_var）

I come from Python background and taking a dive into Java world. I am trying to convert Float to int in Java. Something we do like this in Python int_var = int(float_var)

public class p1 {
    public static void main(String args[]) {
        Integer a = new Integer(5);
        Float b;
        b = new Float(3.14);
        a = (int)b;
        System.out.println(a);
    }
}

产生以下错误 -

Yields the following error -

p1.java:7: error: inconvertible types
        a = (int)b;
                 ^
  required: int
  found:    Float
1 error

推荐答案

使用原始类型，你会没事的：

Use primitives types, and you will be fine:

int a = 5;
float b = 3.14f;  // 3.14 is by default double. 3.14f is float.

a = (int)b;

它不适用于 Wrappers 的原因是那些类型是非-covariant，因此是不兼容的。

The reason it didn't work with Wrappers is those types are non-covariant, and thus are incompatible.

如果你使用整数 types（这里你真的不需要），那么你不应该使用 new 创建Wrapper类型的对象。只需使用自动装箱功能：

And if you are using Integer types (Which you really don't need here), then you should not create Wrapper type objects using new. Just make use of auto-boxing feature:

Integer a = 5;  // instead of `new Integer(5);`

上面的赋值在Java 1.5之后运行，执行自动装箱从 int 原语到整数包装器。它还使JVM能够使用缓存的Integer文字（如果可用），从而防止创建不必要的对象。

the above assignment works after Java 1.5, performing auto-boxing from int primitive to Integer wrapper. It also enables JVM to use cached Integer literals if available, thus preventing creation of unnecessary objects.

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