Find the maximum pair of consecutive valid parenthesis

Consecutive valid parenthesis is when both opening and closing brackets are present just after another and in a consecutive manner. For example {} all are valid and consecutive, hence Consecutive valid parenthesis is 3.

package org.wesome.dsalgo;

import java.util.Stack;

public class ConsecutiveValidParenthesis {
    public static int consecutiveValidParentheses(String s) {
        int maxlen = 0;
        Stack<Integer> stack = new Stack<>();
        stack.push(-1);
        for (int i = 0; i < s.length(); i++) {
            // when encounter '(' push the index onto stack
            if (s.charAt(i) == '(') {
                stack.push(i);
            } else {
                // when encounter ')', pop the topmost element first
                // then subtract the index from the peek element (if the stack is not empty)
                stack.pop();
                if (stack.empty()) {
                    stack.push(i);
                } else {
                    // keep the longest length of the valid substrings
                    maxlen = Math.max(maxlen, i - stack.peek());
                }
            }
        }
        return maxlen;
    }
}

test case

package org.wesome.dsalgo;

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

public class ConsecutiveValidParenthesisTest {
    @Test
    void consecutiveValidParenthesesTest1() {
        String parenthesis = ")()())";
        Assertions.assertEquals(4, ConsecutiveValidParenthesis.consecutiveValidParentheses(parenthesis));
    }

    @Test
    void consecutiveValidParenthesesTest2() {
        String parenthesis = ")()())()";
        Assertions.assertEquals(4, ConsecutiveValidParenthesis.consecutiveValidParentheses(parenthesis));
    }

    @Test
    void consecutiveValidParenthesesTest3() {
        String parenthesis = ")(()())()";
        Assertions.assertEquals(8, ConsecutiveValidParenthesis.consecutiveValidParentheses(parenthesis));
    }
}

build.gradle

plugins {
    id 'java'
}

group = 'org.wesome'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = JavaVersion.VERSION_1_8

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter:5.6.2'
}

test {
    useJUnitPlatform()
}