問(wèn)題描述

我知道這樣的話題被問(wèn)了好幾次，但我的問(wèn)題是關(guān)于完整的 32 位 int 的溢出.例如:

I know such topic was asked several times, but my question is about overflow on full 32 bits of int. For example:

  11111111111111111111111111111111 +
  00000000000000000000000000000001 =
  00000000000000000000000000000000   //overflow!

我發(fā)現(xiàn) topic 有類似的問(wèn)題，但是算法并不完美.

I found topic with similar question about this, however the algorithm is not perfect.

  11111111111111111111111111111111 +
  00000000000000000000000000000000 =
  00000000000000000000000000000000  //overflow!

有沒(méi)有什么簡(jiǎn)單、快速、安全的檢查方法?

Is there any simple, fast, safer way to check this ?

推薦答案

Math.addExact 溢出時(shí)拋出異常

從 Java 8 開始，數(shù)學(xué)類:

Math.addExact throws exception on overflow

Since Java 8 there is a set of methods in the Math class:

• toIntExact(long)
• addExact(int,int)
• subtractExact(int,int)
• multiplyExact(int,int)

……以及長(zhǎng)期版本.

這些方法中的每一個(gè)都會(huì)拋出 ArithmeticException 如果發(fā)生溢出.否則，如果它在范圍內(nèi)，它們會(huì)返回正確的結(jié)果.

Each of these methods throws ArithmeticException if overflow happens. Otherwise they return the proper result if it fits within the range.

加法示例:

int x = 2_000_000_000;
int y = 1_000_000_000;
try {
    int result = Math.addExact(x, y);
    System.out.println("The proper result is " + result);
} catch(ArithmeticException e) {
    System.out.println("Sorry, " + e);
}

查看此在 IdeOne.com 上實(shí)時(shí)運(yùn)行的代碼.

對(duì)不起，java.lang.ArithmeticException:整數(shù)溢出

Sorry, java.lang.ArithmeticException: integer overflow

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