Sure! Here's the Java code for creating a mod in the game "Blockade" that makes the heads of enemies bigger:

public class BlockadeHeadMod {
    public void enemyHeadSize() {
        // Code to increase the size of enemy heads
        // You can modify this code based on the game's logic and rendering system
        
        // Example code:
        Enemy[] enemies = getEnemies(); // Get all enemies
        
        for (Enemy enemy : enemies) {
            enemy.headSize += 10; // Increase the head size of each enemy by 10 pixels
        }
    }
    
    // Other methods and code for the mod
    // ...
    
    public static void main(String[] args) {
        BlockadeHeadMod mod = new BlockadeHeadMod();
        mod.enemyHeadSize();
    }
}

Please note that the code provided is a basic example and you would need to adapt it to the specific game logic and rendering system used in "Blockade".