为什么 DecimalFormat 允许字符作为后缀?

问题描述

我正在使用 DecimalFormat 来解析/验证用户输入.不幸的是，它允许在解析时将字符作为后缀.

I'm using DecimalFormat to parse / validate user input. Unfortunately it allows characters as a suffix while parsing.

示例代码:

try {
  final NumberFormat numberFormat = new DecimalFormat();
  System.out.println(numberFormat.parse("12abc"));
  System.out.println(numberFormat.parse("abc12"));
} catch (final ParseException e) {
  System.out.println("parse exception");
}

结果:

12
parse exception

我实际上希望它们都出现解析异常.如何告诉 DecimalFormat 不允许像 "12abc" 这样的输入?

I would actually expect a parse exception for both of them. How can I tell DecimalFormat to not allow input like "12abc"?

推荐答案

来自NumberFormat.parse:

从给定字符串的开头解析文本以生成一个数字.该方法可能不会使用给定字符串的整个文本.

Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.

这是一个示例，可以让您了解如何确保考虑整个字符串.

Here is an example that should give you an idea how to make sure the entire string is considered.

import java.text.*;

public class Test {
    public static void main(String[] args) {
        System.out.println(parseCompleteString("12"));
        System.out.println(parseCompleteString("12abc"));
        System.out.println(parseCompleteString("abc12"));
    }

    public static Number parseCompleteString(String input) {
        ParsePosition pp = new ParsePosition(0);
        NumberFormat numberFormat = new DecimalFormat();
        Number result = numberFormat.parse(input, pp);
        return pp.getIndex() == input.length() ? result : null;
    }
}

输出:

12
null
null

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