⚡️ Speed up method StringUtils.aspectjNameToPattern by 25%

[codeflash-ai]

📄 25% (0.25x) speedup for StringUtils.aspectjNameToPattern in rewrite-core/src/main/java/org/openrewrite/internal/StringUtils.java

⏱️ Runtime : 775 microseconds → 623 microseconds (best of 139 runs)

📝 Explanation and details

The optimized code caches name.charAt(i + 1) in a local variable next at the start of each iteration instead of calling it twice inside the conditional, and pre-sizes the StringBuilder to Math.max(16, length * 2) to accommodate common expansions (e.g. '.' → "[.$]", '' → "[^.]") without triggering internal resizing. Profiler data shows the hot loop (72.6% of original runtime on name.length() and iteration logic) benefits from eliminating repeated bounds checks and reducing allocation overhead, achieving a 24% runtime improvement (775 µs → 623 µs). The optimization introduces a negligible per-iteration cost for the next assignment but this is more than offset by removing redundant method calls.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 22 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	Coverage data not available

🌀 Click to see Generated Regression Tests

package org.openrewrite.internal;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.openrewrite.internal.StringUtils;

import java.lang.reflect.Constructor;

import static org.junit.jupiter.api.Assertions.*;

public class StringUtilsTest {
    // Instance created via reflection because StringUtils has a private constructor.
    private StringUtils instance;

    @BeforeEach
    void setUp() throws Exception {
        Constructor<StringUtils> ctor = StringUtils.class.getDeclaredConstructor();
        ctor.setAccessible(true);
        instance = ctor.newInstance();
    }

    @Test
    void testSingleAsterisk_AnyType() {
        StringUtils.aspectjNameToPattern("*");
    }

    @Test
    void testEmptyString_ReturnsEmpty() {
        StringUtils.aspectjNameToPattern("");
    }

    @Test
    void testNull_ThrowsNullPointerException() {
        try { StringUtils.aspectjNameToPattern(null); } catch (NullPointerException ignored) {}
    }

    @Test
    void testSimpleQualifiedName_PeriodsReplaced() {
        // Each '.' between identifiers becomes the token [.$]
        String input = "com.example.MyClass";
        String expected = "com[.$]example[.$]MyClass";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testWildcardInIdentifier_AsteriskConverted() {
        // '*' in an identifier becomes [^.]* and dots become [.$]
        String input = "com.*.Foo";
        String expected = "com[.$][^.]*[.$]Foo";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testDoubleDot_SubpackageWildcard() {
        // ".." should be converted into the special subpackage wildcard: \.(.+\.)?
        String input = "com..Foo";
        String expected = "com\\.(.+\\.)?Foo";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testEscapingDollarAndBrackets_Escaped() {
        // ', '[' and ']' should be escaped with a backslash
        String input = "com.Example$Inner[Type]";
        String expected = "com[.$]Example\\$Inner\\[Type\\]";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testEndsWithDot_LastDotPattern() {
        // A trailing '.' should produce the [.$] token
        String input = "com.";
        String expected = "com[.$]";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testStartsWithDot_PrefixPattern() {
        // A leading '.' should produce the [.$] token at the start
        String input = ".MyClass";
        String expected = "[.$]MyClass";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testLargeInput_PerformanceCompletes() {
        // Build a large input by repeating a qualified fragment many times and include some wildcards.
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 2000; i++) {
            if (i > 0) {
                sb.append('.');
            }
            sb.append("com").append(i).append(".example").append(i);
        }
        // append a wildcard identifier at the end to ensure '*' handling in large input
        sb.append(".*.Tail$[X]");
        String largeInput = sb.toString();

        // Ensure the method completes and returns a non-empty pattern of expected minimal size
        try { StringUtils.aspectjNameToPattern(largeInput); } catch (Exception ignored) {}
    }
}

package org.openrewrite.internal;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.lang.reflect.Constructor;

import static org.junit.jupiter.api.Assertions.*;
import org.openrewrite.internal.StringUtils;

public class StringUtilsTest_2 {
    // Although aspectjNameToPattern is static, create an instance via reflection to comply with the test requirements.
    private StringUtils instance;

    @BeforeEach
    void setUp() throws Exception {
        Constructor<StringUtils> ctor = StringUtils.class.getDeclaredConstructor();
        ctor.setAccessible(true);
        instance = ctor.newInstance();
    }

    @Test
    void testSingleAsterisk_ReturnsDotStar() {
        StringUtils.aspectjNameToPattern("*");
    }

    @Test
    void testEmptyString_ReturnsEmptyString() {
        StringUtils.aspectjNameToPattern("");
    }

    @Test
    void testNull_ThrowsNullPointerException() {
        try { StringUtils.aspectjNameToPattern(null); } catch (NullPointerException ignored) {}
    }

    @Test
    void testSimpleName_NoWildcards_ReturnsSame() {
        StringUtils.aspectjNameToPattern("MyClass");
    }

    @Test
    void testDotSeparatedName_ReplacesDotsWithBracketDollar() {
        String input = "com.example.MyClass";
        String expected = "com[.$]example[.$]MyClass";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testStarWildcardInIdentifier_ReplacesWithNotDotStar() {
        String input = "com.example.*";
        String expected = "com[.$]example[.$][^.]*";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testDoubleDotWildcard_TransformsToRegex() {
        String input = "com..*";
        // The method appends the sequence \.(.+\.)? for the double-dot; in a Java literal each backslash is escaped.
        String expected = "com\\.(.+\\.)?[^.]*";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testThreeConsecutiveDots_TransformsEachAppropriately() {
        String input = "a...b";
        // For the second and third dot, the implementation appends the "\\.(.+\\.)?" sequence twice.
        String expected = "a\\.(.+\\.)?\\.(.+\\.)?b";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testSpecialCharacters_EscapedDollarAndBrackets() {
        String input = "com.example.Outer$Inner[Generic]";
        // Dollar, '[' and ']' should be escaped with a backslash in the result.
        String expected = "com[.$]example[.$]Outer\\$Inner\\[Generic\\]";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testLeadingDot_ReplacedWithBracketDollar() {
        String input = ".MyClass";
        String expected = "[.$]MyClass";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testTrailingDot_ReplacedWithBracketDollar() {
        String input = "MyClass.";
        String expected = "MyClass[.$]";
        StringUtils.aspectjNameToPattern(input);
    }

    @Test
    void testLargeInput_PerformanceAndCorrectness() {
        // Build a large input: repeated "a." pairs followed by a star at the end.
        int repeats = 10000;
        StringBuilder in = new StringBuilder(repeats * 2 + 1);
        for (int i = 0; i < repeats; i++) {
            in.append("a.");
        }
        in.append("*");
        String input = in.toString();

        String out = StringUtils.aspectjNameToPattern(input);

        // The output should end with the translation of '*' -> "[^.]*"

        // Count occurrences of the "[.$]" sequence which corresponds to each '.' in the input
        int count = 0;
        String needle = "[.$]";
        int idx = 0;
        while ((idx = out.indexOf(needle, idx)) != -1) {
            count++;
            idx += needle.length();
        }
    }
}

To edit these changes git checkout codeflash/optimize-StringUtils.aspectjNameToPattern-mnn9wbyd and push.