⚡️ Speed up method JavaAssertTransformer._find_balanced_braces by 326% in PR #1199 (omni-java)

[codeflash-ai]

⚡️ This pull request contains optimizations for PR #1199

If you approve this dependent PR, these changes will be merged into the original PR branch omni-java.

This PR will be automatically closed if the original PR is merged.

---

📄 326% (3.26x) speedup for JavaAssertTransformer._find_balanced_braces in codeflash/languages/java/remove_asserts.py

⏱️ Runtime : 13.8 milliseconds → 3.24 milliseconds (best of 182 runs)

📝 Explanation and details

The optimized code achieves a 325% speedup (13.8ms → 3.24ms) by fundamentally changing how it traverses Java code to find balanced braces. Instead of examining every character, it uses strategic jumps to only inspect relevant positions.

Key Optimizations

1. Regex-Based Character Skipping

• Original: Iterates through all 92,057 characters checking each one (char == "'", char == '"', char == "{", char == "}")
• Optimized: Uses self._special_re.search(code, pos) to jump directly to the next special character (', ", {, }), reducing iterations from 92K to 6,905 (~93% reduction)
• Why it's faster: Python's regex engine (written in C) performs substring scanning far more efficiently than Python bytecode loops with repeated character comparisons

2. Efficient String/Char Literal Handling

• Original: Toggles boolean flags (in_string, in_char) and checks them on every iteration
• Optimized: When encountering a quote, uses code.find() to jump directly to the closing quote, then continues from that position
• Why it's faster: A single find() call (C-level string search) replaces potentially hundreds of character-by-character checks

3. Local Variable Caching

• Caches code_len = len(code) and special_re = self._special_re to avoid repeated attribute lookups in the hot loop

Performance Profile

The optimization excels when code contains:

• Long string literals: Test cases with 10,000-character strings show 23,896% speedup (1.34ms → 5.58μs)
• Many quoted sections: 1,000 strings improved by 548% (3.84ms → 592μs), 500 char literals by 358%
• Complex nested structures with quotes: Realistic Java methods improved by 299% (42.5μs → 10.6μs)

Trade-offs appear in edge cases:

• Deeply nested braces without quotes: 1,000-level nesting is 49% slower (327μs → 644μs) because regex search overhead outweighs savings when there are no quotes to skip
• Simple structures: Some small test cases show 8-50% slowdown due to regex setup cost

Impact Assessment

Since _find_balanced_braces is part of JavaAssertTransformer (used to analyze Java test code structure), the optimization significantly benefits workloads involving:

• Parsing Java files with extensive string literals (common in test assertions)
• Processing large codebases where this method is called frequently
• Real-world Java code (the realistic method test shows strong gains)

The 325% overall speedup indicates the benchmark workload closely matches typical Java test code patterns where quoted content is prevalent.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 105 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Click to see Generated Regression Tests

import pytest  # used for our unit tests
from codeflash.languages.java.remove_asserts import JavaAssertTransformer

def test_basic_single_level_braces():
    # Create a real transformer instance (requires only a function name).
    t = JavaAssertTransformer("m")
    # Simple code with a single pair of braces.
    code = "class X { int a = 1; } // tail"
    open_pos = code.index("{")  # position of the opening brace
    # Call the real instance method (don't pass self manually).
    content, next_pos = t._find_balanced_braces(code, open_pos) # 3.47μs -> 3.47μs (0.000% faster)

def test_nested_braces_return_inner_text_and_position():
    t = JavaAssertTransformer("fn")
    code = "x { a { b() {}; } end } trailing"
    open_pos = code.index("{")
    content, next_pos = t._find_balanced_braces(code, open_pos) # 4.64μs -> 5.49μs (15.5% slower)

def test_open_pos_not_brace_returns_none_and_negative_one():
    t = JavaAssertTransformer("f")
    code = "no braces here"
    # open_brace_pos is within bounds but not pointing at '{'
    content, pos = t._find_balanced_braces(code, 3) # 621ns -> 611ns (1.64% faster)

def test_open_pos_out_of_bounds_returns_none_and_negative_one():
    t = JavaAssertTransformer("g")
    code = "short {}"
    # Position past the end should be invalid
    content, pos = t._find_balanced_braces(code, len(code) + 5) # 451ns -> 420ns (7.38% faster)

def test_unmatched_open_brace_returns_none_and_negative_one():
    t = JavaAssertTransformer("h")
    # Missing closing brace -> should indicate failure
    code = "start { inner { still open "
    open_pos = code.index("{")
    content, pos = t._find_balanced_braces(code, open_pos) # 4.20μs -> 3.31μs (27.0% faster)

def test_braces_inside_double_quoted_string_ignored_for_depth():
    t = JavaAssertTransformer("quotes")
    # Inner braces inside the quoted string should not affect brace matching.
    code = 'A { "this { is } inside string" ; } after'
    open_pos = code.index("{")
    content, pos = t._find_balanced_braces(code, open_pos) # 5.94μs -> 4.52μs (31.5% faster)

def test_escaped_double_quote_inside_string_preserves_string_mode():
    t = JavaAssertTransformer("esc")
    # The string contains an escaped quote (\") and a brace after it; escaped quote should not end the string.
    code = 'X { "escaped \\" { still in string \\" done" ; } rest'
    open_pos = code.index("{")
    content, pos = t._find_balanced_braces(code, open_pos) # 7.17μs -> 4.88μs (47.0% faster)

def test_char_literals_with_brace_are_ignored_for_depth():
    t = JavaAssertTransformer("char")
    # A char literal contains a brace; in_char toggling should prevent this brace from affecting depth.
    code = "z { char c = '{'; ; } end"
    open_pos = code.index("{")
    content, pos = t._find_balanced_braces(code, open_pos) # 4.40μs -> 4.30μs (2.35% faster)

def test_escaped_single_quote_in_char_literal_does_not_terminate_char_mode():
    t = JavaAssertTransformer("charesc")
    # Char literal with escaped single quote: '\'' (written in Python string with escapes).
    # The function checks only the immediate prev_char against backslash, so an escaped quote should not toggle incorrectly.
    code = "A { char c = '\\''; int x = 1; } tail"
    open_pos = code.index("{")
    content, pos = t._find_balanced_braces(code, open_pos) # 5.73μs -> 4.75μs (20.7% faster)

def test_many_nested_braces_large_scale_1000_levels():
    t = JavaAssertTransformer("big")
    # Create 1000 nested opening braces followed by 1000 closing braces.
    n = 1000
    code = "X " + "{" * n + "}" * n + " done"
    open_pos = code.index("{")  # first opening brace
    content, pos = t._find_balanced_braces(code, open_pos) # 327μs -> 644μs (49.1% slower)
    # The content should be all inner characters between the outermost braces.
    # Expected content length: total braces (=2n) plus 'X ' removed; specifically inner part is (2n - 2) between first and last brace
    expected_inner_open = "{" * (n - 1)
    expected_inner_close = "}" * (n - 1)
    # Position should point to the character after the final closing brace
    final_closing_index = code.index("}") + (n - 1)  # first '}' index plus n-1 further

def test_many_braces_with_strings_and_chars_large_scale():
    t = JavaAssertTransformer("mixed_big")
    # Build a large structure mixing braces and quoted segments that include braces.
    # We repeat a pattern many times to reach a sizeable input.
    pattern = '{ "{" \'{\' {} }'.format  # will use format to insert dynamic content
    # Construct by repeating a safe small fragment with inner braces inside quotes.
    fragment = '{ "inner {ignored}" \'x\' }'
    repeat = 300  # moderate large number to exercise loops without being too slow
    code = "S " + fragment * repeat + " trailing"
    open_pos = code.index("{")
    content, pos = t._find_balanced_braces(code, open_pos) # 5.70μs -> 5.28μs (7.95% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

import pytest
from codeflash.languages.java.parser import JavaAnalyzer
from codeflash.languages.java.remove_asserts import JavaAssertTransformer

# Test fixtures
@pytest.fixture
def transformer():
    """Create a JavaAssertTransformer instance for testing."""
    return JavaAssertTransformer(function_name="testMethod")

class TestFindBalancedBraces:
    """Test suite for JavaAssertTransformer._find_balanced_braces method."""

    # ============================================================================
    # Basic Tests - Fundamental functionality under normal conditions
    # ============================================================================

    def test_simple_empty_braces(self, transformer):
        """Test finding balanced braces with empty content."""
        code = "{ }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 1.98μs -> 3.23μs (38.5% slower)

    def test_simple_content_in_braces(self, transformer):
        """Test finding balanced braces with simple content."""
        code = "{ int x = 5; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 3.37μs -> 3.20μs (5.32% faster)

    def test_nested_braces(self, transformer):
        """Test finding balanced braces with nested braces."""
        code = "{ { int x = 5; } }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.08μs -> 4.60μs (11.3% slower)

    def test_multiple_nested_levels(self, transformer):
        """Test finding balanced braces with multiple nesting levels."""
        code = "{ { { int x = 5; } } }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.77μs -> 5.25μs (9.16% slower)

    def test_braces_at_offset_position(self, transformer):
        """Test finding balanced braces starting at an offset position."""
        code = "int x = { int y = 3; }"
        content, end_pos = transformer._find_balanced_braces(code, 8) # 3.41μs -> 3.16μs (7.95% faster)

    def test_string_with_braces_inside(self, transformer):
        """Test that braces inside strings are not counted."""
        code = '{ String s = "{ }"; }'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.72μs -> 4.59μs (2.86% faster)

    def test_char_with_braces_inside(self, transformer):
        """Test that braces inside char literals are not counted."""
        code = "{ char c = '{'; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.17μs -> 4.53μs (7.97% slower)

    def test_string_with_escaped_quote(self, transformer):
        """Test handling of escaped quotes in strings."""
        code = r'{ String s = "\""; }'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.69μs -> 4.67μs (0.407% faster)

    def test_method_with_curly_braces_in_body(self, transformer):
        """Test method body with multiple statement blocks."""
        code = "{ if (true) { x = 1; } else { x = 2; } }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 7.29μs -> 5.60μs (30.2% faster)

    # ============================================================================
    # Edge Tests - Extreme or unusual conditions
    # ============================================================================

    def test_not_opening_brace_at_position(self, transformer):
        """Test when position does not point to an opening brace."""
        code = "int x = { int y; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 631ns -> 622ns (1.45% faster)

    def test_position_beyond_string_length(self, transformer):
        """Test when position is beyond the string length."""
        code = "{ int x; }"
        content, end_pos = transformer._find_balanced_braces(code, 100) # 470ns -> 481ns (2.29% slower)

    def test_unbalanced_braces_missing_closing(self, transformer):
        """Test when there are unbalanced braces (missing closing brace)."""
        code = "{ int x = 5; int y = 6;"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.39μs -> 1.61μs (172% faster)

    def test_unbalanced_braces_extra_opening(self, transformer):
        """Test when there are unbalanced braces (extra opening brace)."""
        code = "{ { int x = 5; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 3.65μs -> 4.01μs (8.98% slower)

    def test_empty_string(self, transformer):
        """Test with empty string."""
        code = ""
        content, end_pos = transformer._find_balanced_braces(code, 0) # 481ns -> 481ns (0.000% faster)

    def test_single_opening_brace(self, transformer):
        """Test with single opening brace and nothing else."""
        code = "{"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 862ns -> 871ns (1.03% slower)

    def test_position_equals_string_length(self, transformer):
        """Test when position is exactly at string length."""
        code = "{ int x; }"
        content, end_pos = transformer._find_balanced_braces(code, len(code)) # 461ns -> 451ns (2.22% faster)

    def test_consecutive_braces(self, transformer):
        """Test finding balanced braces with consecutive brace pairs."""
        code = "{}{}{}}"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 1.65μs -> 3.33μs (50.3% slower)

    def test_string_with_escaped_backslash_before_quote(self, transformer):
        """Test handling of escaped backslash followed by quote."""
        code = r'{ String s = "\\\""; }'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 5.05μs -> 5.14μs (1.75% slower)

    def test_single_char_literal(self, transformer):
        """Test with single character in char literal."""
        code = "{ char c = 'x'; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.23μs -> 4.55μs (7.06% slower)

    def test_char_literal_with_escaped_char(self, transformer):
        """Test char literal containing escaped character."""
        code = "{ char c = '\\''; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.40μs -> 4.78μs (7.99% slower)

    def test_multiple_string_literals(self, transformer):
        """Test multiple string literals in sequence."""
        code = '{ String s1 = "a"; String s2 = "b"; }'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 6.98μs -> 5.58μs (25.1% faster)

    def test_string_with_single_quote_inside(self, transformer):
        """Test string containing single quotes."""
        code = """{ String s = "it's"; }"""
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.95μs -> 4.59μs (7.87% faster)

    def test_char_with_single_space(self, transformer):
        """Test char literal with single space."""
        code = "{ char c = ' '; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 4.14μs -> 4.50μs (8.03% slower)

    def test_very_deeply_nested_braces(self, transformer):
        """Test with 10 levels of nesting."""
        code = "{ { { { { { { { { { } } } } } } } } } } }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 7.19μs -> 9.97μs (27.8% slower)

    def test_first_char_not_brace(self, transformer):
        """Test when first character at position is not a brace."""
        code = " { int x; }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 581ns -> 631ns (7.92% slower)

    def test_position_points_to_closing_brace(self, transformer):
        """Test when position points to a closing brace instead of opening."""
        code = "{ int x; }"
        content, end_pos = transformer._find_balanced_braces(code, 9) # 561ns -> 592ns (5.24% slower)

    def test_string_with_newline(self, transformer):
        """Test string literal containing newline."""
        code = '{ String s = "line1\nline2"; }'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 5.83μs -> 4.72μs (23.6% faster)

    def test_adjacent_strings_no_space(self, transformer):
        """Test two string literals next to each other (Java string concatenation)."""
        code = '{ String s = "a" "b"; }'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 5.13μs -> 5.33μs (3.75% slower)

    # ============================================================================
    # Large-Scale Tests - Performance and scalability
    # ============================================================================

    def test_large_nested_structure_100_levels(self, transformer):
        """Test with 100 levels of nesting."""
        # Build a code string with 100 nested braces
        code = "{ " * 100 + "int x = 1;" + " }" * 100
        content, end_pos = transformer._find_balanced_braces(code, 0) # 64.7μs -> 67.9μs (4.66% slower)

    def test_large_code_with_many_strings(self, transformer):
        """Test with many string literals (1000 strings)."""
        # Build code with 1000 string declarations
        strings = " ".join([f'String s{i} = "value{i}";' for i in range(1000)])
        code = "{ " + strings + " }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 3.84ms -> 592μs (548% faster)

    def test_large_code_with_many_char_literals(self, transformer):
        """Test with many char literals (500 chars)."""
        chars = " ".join([f"char c{i} = 'x';" for i in range(500)])
        code = "{ " + chars + " }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 1.31ms -> 285μs (358% faster)

    def test_large_nested_if_statements(self, transformer):
        """Test with deeply nested if statements (100 levels)."""
        code = "{ "
        for i in range(100):
            code += f"if (x{i} > 0) {{ "
        code += "int result = 1;"
        for i in range(100):
            code += " }"
        code += " }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 265μs -> 76.7μs (246% faster)

    def test_large_code_with_mixed_quotes(self, transformer):
        """Test with alternating string and char literals (500 of each)."""
        code = "{ "
        for i in range(500):
            code += f'String s{i} = "str{i}"; char c{i} = \'x\'; '
        code += "}"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 3.07ms -> 593μs (418% faster)

    def test_very_long_string_literal(self, transformer):
        """Test with a very long string literal (10000 characters)."""
        long_string_content = "a" * 10000
        code = f'{{ String s = "{long_string_content}"; }}'
        content, end_pos = transformer._find_balanced_braces(code, 0) # 1.34ms -> 5.58μs (23896% faster)

    def test_large_code_multiple_method_bodies(self, transformer):
        """Test with multiple nested method-like structures (100 methods)."""
        code = "{ "
        for i in range(100):
            code += f"{{ int method{i} = {i}; }} "
        code += "}"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 353μs -> 82.3μs (330% faster)

    def test_offset_at_various_positions_in_large_code(self, transformer):
        """Test finding balanced braces at different offset positions in large code."""
        code = "int x = { { { int y = 5; } } }; int z = { int w = 10; };"
        # Find braces at offset 8 (first nested structure)
        content1, end_pos1 = transformer._find_balanced_braces(code, 8) # 4.81μs -> 5.51μs (12.7% slower)

        # Find braces at offset 41 (second structure)
        content2, end_pos2 = transformer._find_balanced_braces(code, 41) # 371ns -> 410ns (9.51% slower)

    def test_alternating_string_and_brace_escape_sequences(self, transformer):
        """Test with complex escape sequences in strings (500 strings with escapes)."""
        code = "{ "
        for i in range(500):
            code += rf'String s{i} = "test\n\t\r\\"; '
        code += "}"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 2.18ms -> 286μs (659% faster)

    def test_large_sequential_nested_pairs(self, transformer):
        """Test with 500 sequential nested brace pairs."""
        code = ""
        for i in range(500):
            code += "{ "
        code += "int x = 1;"
        for i in range(500):
            code += " }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 316μs -> 329μs (3.79% slower)

    def test_code_with_realistic_java_method(self, transformer):
        """Test with realistic Java method containing loops and conditions."""
        code = """{
            for (int i = 0; i < 1000; i++) {
                if (i % 2 == 0) {
                    String s = "even";
                } else {
                    String s = 'o';
                }
                int[] arr = new int[]{1, 2, 3};
            }
        }"""
        content, end_pos = transformer._find_balanced_braces(code, 0) # 42.5μs -> 10.6μs (299% faster)

    def test_performance_with_many_adjacent_strings(self, transformer):
        """Performance test: 100 adjacent strings with quotes."""
        code = "{ " + " ".join([f'"{chr(97 + i % 26)}"' for i in range(100)]) + " }"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 61.0μs -> 52.1μs (16.9% faster)

    def test_large_code_complex_escape_patterns(self, transformer):
        """Test with complex escape patterns in 100 strings."""
        code = "{ "
        for i in range(100):
            code += f'String s{i} = "\\u0041\\n\\t\\r\\\\"; '
        code += "}"
        content, end_pos = transformer._find_balanced_braces(code, 0) # 448μs -> 63.9μs (602% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-pr1199-2026-02-21T00.24.27 and push.

[claude]

PR Review Summary

Prek Checks

✅ Passed — No issues in the changed file (codeflash/languages/java/remove_asserts.py).

Note: 3 F401 (unused-import) warnings exist in codeflash/languages/registry.py from the parent omni-java branch. These are side-effect imports required for language registration and should use # noqa: F401 — not addressed in this optimization PR.

Mypy

✅ Passed — No type errors found.

Code Review

✅ No critical issues found.

The optimization replaces character-by-character iteration with regex-based jumping (re.search + str.find) in _find_balanced_braces. The behavioral changes are:

• Uses precompiled _special_re = re.compile(r"[\"'{}]") to skip non-special characters in C rather than Python bytecode
• String/char literal regions are skipped using str.find() for closing quotes instead of boolean state flags
• Both approaches share the same single-char escape check limitation (prev_char \!= "\\") which does not handle double-escaped backslashes, but this is a pre-existing behavior, not a regression

All 157 existing tests pass on both the original and optimized versions.

Test Coverage

File	Base (omni-java)	PR	Change
codeflash/languages/java/remove_asserts.py	88% (447 stmts, 55 missed)	86% (457 stmts, 63 missed)	-2%

The slight coverage decrease (88% → 86%) is expected — the optimized code has 10 additional statements from the restructured control flow (regex match + find-based literal skipping), and 8 of those new paths (e.g., find() returning -1 for unclosed literals) are not hit by the existing test suite. This is a minor and acceptable change for an optimization PR.

---

Last updated: 2026-02-21