如何刪除字符串中$之后的空格？

Question

我有一個輸入，$和值之間有一個空格，我想刪除空格。 這段代碼：

System.out.println("This costs $ 5 even.".replaceAll("\\$ ", "$"));

應該打印出來：

This costs $5 even.

但它拋出一個異常：

Illegal group reference: group index is missing
java.lang.IllegalArgumentException
    at java.util.regex.Matcher.appendReplacement(Matcher.java:819)
    at java.util.regex.Matcher.replaceAll(Matcher.java:955)
    at java.lang.String.replaceAll(String.java:2223)
    at DollarTest.test(DollarTest.java:18)

我想念什么？

Answer 1

只需使用replace() ：

System.out.println("This costs $ 5 even.".replace("$ ", "$"));

Answer 2

問題在於，在正則表達式替換字符串中， $是特殊的。 應該使用它來指代正則表達式本身的捕獲組。

您需要對其進行轉義：

.replaceAll("\\$ ", "\\$")

但是正如@pp_所提到的 ，最好在這里使用普通的.replace() 。

Answer 3

另一種選擇-將$和值分組在空格周圍，然后在替換中合並它們。

String s = "This costs $ 5 even. That costs $ 6 even. This is a $ sign.";
System.out.println(s.replaceAll("(\\$)\\s(\\d+)", "$1$2"));

輸出量

This costs $5 even. That costs $6 even. This is a $ sign.

它還指出了其他答案中的缺陷

String s = "This costs $ 5 even. That costs $ 6 even. This is a $ sign.";
System.out.println(s.replaceAll("\\$ ", "\\$"));

輸出"$sign" 。

This costs $5 even. That costs $6 even. This is a $sign.

Answer 4

我建議您使用以下正則表達式刪除$和下一個數字之間的任意數量的空格。

try {
    String data = "This costs $          7 even";
    String resultString = data.replaceAll("(?is)(?<=\\$)\\s*(?=\\d+)", "");
    System.out.println(resultString);

} catch (PatternSyntaxException ex) {

}

輸入：

This costs $ 5 even
This costs $6 even
This costs $          7 even
This costs $          77 even
This costs $          7.2 even
This costs $          0.21 even
It's cost is between $   5.2 and $   8.3
You don't have to pay top $ for this.

輸出：

This costs $5 even
This costs $6 even
This costs $7 even
This costs $77 even
This costs $7.2 even
This costs $0.21 even
It's cost is between $5.2 and $8.3
You don't have to pay top $ for this.