Fast threadsafe insert only random access circular buffer

CircularBuffer.java

import java.util.RandomAccess;

/**
 * Fast threadsafe insert only random access circular buffer
 */
public class CircularBuffer<T> implements RandomAccess {

    private final Object[] items;
    private int head = 0;
    private boolean isPopulated = false;

    public CircularBuffer(int size) {
        if (size <= 0) {
            throw new IllegalArgumentException();
        }
        this.items = new Object[size];
    }

    public synchronized void add(T value) {
        items[head++] = value;
        if (head == items.length) {
            head = 0;
            isPopulated = true;
        }
    }

    public T get(int index) {
        if (index < 0 || index >= size()) {
            throw new ArrayIndexOutOfBoundsException(index);
        }
        //noinspection unchecked
        return (T) items[index];
    }

    public int size() {
        return isPopulated ? items.length : head;
    }
}