我正在做一个池应用程序，其中有3个变量，a为初始连接，它是20，b为递增大小，这意味着当池达到20时，它将增加池大小的5乘5，y为最大连接数，它是50，我有问题实现b变量在一个有条件的方式，这是代码

public class ThreadHolder extends Thread {
ArrayList<Client> pool;
public static int a = 20;
public static int b = 5;
public static int y = 50;
public static long ftime, stime, time;
public Client c = null;

public ThreadHolder(){
    pool = new ArrayList<Client>();
}

public void run(){
    stime = System.currentTimeMillis();
    try {
        while(pool.size()<= y){     
            if(pool.size() < a){    
                poolHelper();
                Thread.sleep(600);
            }

            else if(pool.size()> a){
                a = a+b;
                poolHelper();
                Thread.sleep(600);
            }   

            else {
                System.out.println("----------------------------------");
                System.out.println("Database is busy, please try again in a second.");  
                deleteClient(c);
                System.out.println("Pool -> "+pool.size() + ".");
                Thread.sleep(300);
        }   

        ftime = System.currentTimeMillis();
        time = (ftime - stime)/1000 ;
        System.out.println("Time established -> " + time + " sec");
        }   
    }catch(Exception e) {e.printStackTrace();}
}

public void poolHelper(){
    obtainClient(c);
    addClient(c);
    System.out.println("Pool -> "+pool.size() + ".");
}

public synchronized void obtainClient(Client c){
    Client a = new Client(this);
    a.start();
}

public synchronized void addClient(Client c){
    pool.add(c);
}

public synchronized void deleteClient(Client c){
    pool.remove(c);
}

}
当我的池大小达到20个连接以上时，如何实现使用b来不断向池中添加客户端