Java 中的 replace() 和 replaceAll() [英] replace() and replaceAll() in Java

问题描述

以下代码使用Java中String类的replace()方法.

The following code uses the replace() method of the String class in Java.

String a = "abc/xyz";
System.out.println(a.replace("/", "\\"));

给定字符串 a 中的

/ 被替换为 \.

/ in the given String a is being replaced with \.

同样的事情是错误的，如果我们使用replaceAll()方法如下.

The same thing is wrong, if we use the replaceAll() method as follows.

System.out.println(a.replaceAll("/", "\\"));

它会导致抛出异常 java.lang.StringIndexOutOfBoundsException.它需要两个额外的反斜杠 \，如下所示，因为 replaceAll() 使用正则表达式，而 replace() 方法不是这种情况.

It causes the exception java.lang.StringIndexOutOfBoundsException to be thrown. It requires two additional backslashes \ like the following, since replaceAll() uses a regex which is not the case with the replace() method.

System.out.println(a.replaceAll("/", "\\\\"));

唯一的问题是为什么这个方法在只使用两个斜线时会像这样 a.replaceAll("/", "\\") 抛出 java.lang.StringIndexOutOfBoundsException?

The only question is why does this method when used with only two slashes like this a.replaceAll("/", "\\") throw java.lang.StringIndexOutOfBoundsException?

另一方面，split() 方法最初发出警告无效的正则表达式:意外的内部错误(我使用的是 NetBeans 6.9.1).>

The split() method on the other hand initially issues a waring Invalid regular expression: Unexpected internal error (I'm using NetBeans 6.9.1).

String b="abc\\xyz";
System.out.println(b.split("\\")[0]+b.split("\\")[1]); //Issues a warning as specified.

尝试运行它会导致抛出异常 java.util.regex.PatternSyntaxException.

An attempt to run this causes the exception java.util.regex.PatternSyntaxException to be thrown.

因为它使用了像 replaceAll() 这样的正则表达式，所以它需要四个反斜杠.

Since it uses a regex like replaceAll(), it requires four back slashes.

System.out.println(b.split("\\\\")[0]+b.split("\\\\")[1]);

为什么 a.replaceAll("/", "\\\\"); 在前面的例子中没有发出这样的警告或这样的运行时异常，即使它有无效模式?

Why does a.replaceAll("/", "\\\\"); as in the preceding case not issue such a warning or such a run time exception, even though it has an invalid pattern?

推荐答案

来自 Javadoc String.replaceAll

From Javadoc String.replaceAll

请注意，替换字符串中的反斜杠 (\) 和美元符号 ($) 可能会导致结果与将其视为文字替换字符串时的结果不同；参见 Matcher.replaceAll.如果需要，使用 Matcher.quoteReplacement(java.lang.String) 抑制这些字符的特殊含义.

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

System.out.println(a.replaceAll("/", Matcher.quoteReplacement("\\")));

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