java.util.regex.PatternSyntaxException:Dangling Meta character ' * ' near index 0

Use the Repalceall method to appear java.util.regex.PatternSyntaxException:Dangling meta character ' * ' near index 0 exception

The code is as follows:

1     @Test 2      Public void Testreplaceall () {3         String sql = "SELECT * from Per_handle where ID not in (' 3ce7405509414105a65e7456987e7393 ')";         4          String countsql = Sql.replaceall ("*", "count (*)"); 5 6         System.out.println (countsql); 7     }    

The following error was reported after running in JUnit test mode:

java.util.regex.PatternSyntaxException:Dangling Meta character ' * ' near index 0

This error is related to the Repalceall method, and the ReplaceAll method structure can be seen in the Java API documentation as follows:

String Java.lang.String.replaceAll (string regex, string replacement)

Replaces this string with the given replacement for all substrings that match the given regular expression.

The first argument is a regular expression, and the second argument is the replaced string.

Because "*" has a special meaning in regular expressions, it results in an error.

Two workarounds are attempted:

1, the "*" to escape processing, so that it becomes a normal character

1 @Test 2  Public void Testreplaceall () {3     String sql = "SELECT * from Per_handle where ID not in (' 3ce7405509414105a65e7456987e7393 ')";         4     String countsql = Sql.replaceall ("\\*", "Count (*)"); 5     System.out.println (countsql); 6 }

2. Replace ReplaceAll method with replace method

1 @Test 2  Public void Testreplaceall () {3     String sql = "SELECT * from Per_handle where ID not in (' 3ce7405509414105a65e7456987e7393 ')";         4     String countsql = Sql.replace ("*", "count (*)"); 5     System.out.println (countsql); 6 }

The reasons for this approach to success are:

String Java.lang.String.replace (charsequence target, charsequence replacement)

The first argument of the Replace method is a character or string, so "*" is treated as a normal string by default.

Java.util.regex.PatternSyntaxException:Dangling Meta character ' * ' near index 0