java.lang.StackOverflowError means the call stack exceeded its size limit — usually from infinite recursion.

What causes this error

1. Infinite recursion — a method calls itself without a proper base case
2. Circular references — A calls B, B calls A
3. Very deep recursion — legitimate recursion that’s too deep for the stack

Fix 1: Add or fix the base case

// ❌ No base case — infinite recursion
int factorial(int n) {
    return n * factorial(n - 1);
}

// ✅ Base case stops recursion
int factorial(int n) {
    if (n <= 1) return 1;
    return n * factorial(n - 1);
}

Fix 2: Convert recursion to iteration

// ✅ Iterative — no stack overflow risk
int factorial(int n) {
    int result = 1;
    for (int i = 2; i <= n; i++) {
        result *= i;
    }
    return result;
}

Fix 3: Increase stack size (last resort)

java -Xss4m MyApp  # Increase stack to 4MB (default ~512KB)

How to find the recursion

The stack trace shows the same method name repeated hundreds of times. Look at that method and find where it calls itself.

Related: Java cheat sheet · Java: OutOfMemoryError fix · Stack Overflow Error fix