如何在Java（JDK 7）中获取字符串中指定字符或固定前缀后的文本内容？

Hey there! Let's break down how to get the text after that fixed exception prefix in Java 7 — since you've got a specific string to work with, we can use simple, reliable methods built right into the JDK.

Approach 1: Using indexOf() + substring() (Recommended for Fixed Prefixes) #

This method is super efficient because we know the exact prefix, so we can skip straight to the content we need without unnecessary searching.

public class ExceptionMessageExtractor {
    public static void main(String[] args) {
        String errorString = "com.microsoft.sqlserver.jdbc.SQLServerException: User not found";
        String fixedPrefix = "com.microsoft.sqlserver.jdbc.SQLServerException:";
        
        // Quick check to make sure the prefix exists (safe even if you say it's fixed!)
        if (errorString.startsWith(fixedPrefix)) {
            // Jump past the prefix by using its length as the start index
            String extractedMessage = errorString.substring(fixedPrefix.length());
            // Trim leading whitespace (your example has a space after the colon — this cleans it up)
            extractedMessage = extractedMessage.trim();
            System.out.println(extractedMessage); // Output: User not found
        } else {
            // Handle edge case where the prefix is missing (adjust based on your needs)
            System.err.println("Expected prefix not found in the input string");
        }
    }
}

Why this works: #

• fixedPrefix.length() gives us the exact number of characters in the prefix. Calling substring() with this value starts our new string right after the prefix ends.
• The optional trim() call removes any leading whitespace (like the space after the colon in your example) to give you a clean, usable error message.

Approach 2: Using split() #

If you prefer a more concise approach (though slightly less efficient for fixed prefixes), you can split the string on the prefix and grab the second part of the result.

public class ExceptionMessageExtractor {
    public static void main(String[] args) {
        String errorString = "com.microsoft.sqlserver.jdbc.SQLServerException: User not found";
        String fixedPrefix = "com.microsoft.sqlserver.jdbc.SQLServerException:";
        
        // Split into max 2 parts so we don't waste time splitting further
        String[] stringParts = errorString.split(fixedPrefix, 2);
        if (stringParts.length == 2) {
            String extractedMessage = stringParts[1].trim();
            System.out.println(extractedMessage); // Output: User not found
        } else {
            System.err.println("Expected prefix not found in the input string");
        }
    }
}

Note: #

• The 2 in split(fixedPrefix, 2) ensures we only split the string once, which is more efficient than splitting all possible occurrences (though in your case, there's only one).
• Again, trim() helps clean up any leading whitespace after the colon.

Quick JDK 7 Reminder: #

Both methods use core JDK 7 features — no need for Java 8+ streams or external libraries. Always include that prefix check to avoid StringIndexOutOfBoundsException if your input ever deviates from the expected format.

内容的提问来源于stack exchange，提问作者Julian Gimenez