如何在java中将字符串转换为整数时检测溢出 [英] How to detect overflow when convert string to integer in java

问题描述

如果我想在java
中将字符串转换为int，你知道我是否有办法检测溢出？
我的意思是字符串文字实际上代表一个大于MAX_INT的值？

if I want to convert a string into an int in java do you know if there is a way for me to detect overflow? by that I mean the string literal actually represents a value which is larger than MAX_INT?

java doc没有提到它..
it只是说如果字符串不能被解析为整数，它将通过FormatException
没有提到关于溢出的一个词。

java doc didn't mention it.. it just says that if the string can not be parsed as an integer, it will through FormatException didn't mention a word about overflow..

推荐答案

如果我想在java中将字符串转换为int，你知道我是否有办法检测溢出？

是的。捕获解析异常将是正确的方法，但这里的难点是 Integer.parseInt（String s） 抛出 NumberFormatException for 任何解析错误，包括溢出。您可以通过查看JDK的 src.zip 文件中的Java源代码进行验证。幸运的是，存在一个构造函数 BigInteger（String s） 将抛出相同的解析异常，除之外的范围限制异常，因为 BigInteger s没有界限。我们可以使用这些知识来捕获溢出情况：

Yes. Catching parse exceptions would be the correct approach, but the difficulty here is that Integer.parseInt(String s) throws a NumberFormatException for any parse error, including overflow. You can verify by looking at the Java source code in the JDK's src.zip file. Luckily, there exists a constructor BigInteger(String s) that will throw identical parse exceptions, except for range limitation ones, because BigIntegers have no bounds. We can use this knowledge to trap the overflow case:

/**
 * Provides the same functionality as Integer.parseInt(String s), but throws
 * a custom exception for out-of-range inputs.
 */
int parseIntWithOverflow(String s) throws Exception {
    int result = 0;
    try {
        result = Integer.parseInt(s);
    } catch (Exception e) {
        try {
            new BigInteger(s);
        } catch (Exception e1) {
            throw e; // re-throw, this was a formatting problem
        }
        // We're here iff s represents a valid integer that's outside
        // of java.lang.Integer range. Consider using custom exception type.
        throw new NumberFormatException("Input is outside of Integer range!");
    }
    // the input parsed no problem
    return result;
}

如果你真的需要为仅定制输入超过Integer.MAX_VALUE，你可以在抛出自定义异常之前，使用@ Sergej的建议。如果上面是过度杀戮并且您不需要隔离溢出的情况，只需通过捕获它来抑制异常：

If you really need to customize this for only inputs exceeding Integer.MAX_VALUE, you can do that just before throwing the custom exception, by using @Sergej's suggestion. If above is overkill and you don't need to isolate the overflow case, just suppress the exception by catching it:

int result = 0;
try {
    result = Integer.parseInt(s);
} catch (NumberFormatException e) {
    // act accordingly
}

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