問題描述

我正在使用 DecimalFormat 來解析/驗證用戶輸入.不幸的是，它允許在解析時將字符作為后綴.

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

示例代碼:

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");
}

結果:

12
parse exception

我實際上希望它們都出現解析異常.如何告訴 DecimalFormat 不允許像 "12abc" 這樣的輸入?

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

推薦答案

來自NumberFormat.parse:

從給定字符串的開頭解析文本以生成一個數字.該方法可能不會使用給定字符串的整個文本.

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.

這是一個示例，可以讓您了解如何確保考慮整個字符串.

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;
    }
}

輸出:

12
null
null

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