Java String Manipulation: Multiple Approaches to Remove First and Last Characters

Problem Background and Requirements Analysis

In web service development, it is common to handle data formats returned by SOAP messages. As shown in the example, the LoginToken value obtained from the web service is wrapped in square brackets [ and ], and these decorative characters need to be removed for practical use.

Core Solution: substring Method

The substring method based on string indexing is the most direct and effective solution. This method extracts a substring by specifying start and end indices.

String loginToken = "[wdsd34svdf]";
String result = loginToken.substring(1, loginToken.length() - 1);
System.out.println(result); // Output: wdsd34svdf

Code Analysis:

• substring(1, loginToken.length() - 1) starts extraction from index 1
• Index 1 corresponds to the second character, skipping the initial [
• The end index is length() - 1, excluding the final ]
• Java string indices start at 0, length() returns the string length

In-depth Method Principle Analysis

The substring method in Java operates based on character arrays with O(1) time complexity. Its internal implementation directly references the specified interval of the original character array, avoiding unnecessary memory copying.

Key points of index calculation:

// Assuming the string is "[token]"
// Indices: 0 1 2 3 4 5 6
// Characters: [ t o k e n ]
// substring(1, 6) → "token"

Boundary Case Handling

Various boundary scenarios need consideration in practical applications:

// Empty string handling
if (loginToken != null && loginToken.length() > 2) {
    result = loginToken.substring(1, loginToken.length() - 1);
} else {
    result = loginToken;
}

// Dynamic character detection
if (loginToken.startsWith("[") && loginToken.endsWith("]")) {
    result = loginToken.substring(1, loginToken.length() - 1);
}

Alternative Approach Comparison

Besides the substring method, other viable technical solutions exist:

Regular Expression Method

String result = loginToken.replaceAll("^\\[|\\]$", "");

Apache Commons Lang

import org.apache.commons.lang3.StringUtils;
String result = StringUtils.substring(loginToken, 1, -1);

Performance Optimization Recommendations

In performance-sensitive scenarios:

• The substring method offers optimal performance, suitable for high-frequency calls
• Regular expressions are appropriate for complex pattern matching but incur significant performance overhead
• Third-party libraries provide additional functionality but increase dependency costs

Practical Application Extensions

This technique can be extended to other similar scenarios:

• Processing quote-wrapped JSON strings
• Cleaning XML tag content
• Removing special characters from CSV data

By systematically mastering string manipulation methods, data processing efficiency and code quality can be significantly enhanced.