针对对象成员的变量统计

我想请教一下，我这里写了一个银行账户的代码，我可以做到一些基本的功能，但是要是做一个用账户号码查询余额的方法应该怎么写

package examination;

public class study3 {
private String ID;
private int number;
private int balance;

public study3(String iD) {
    ID = iD;
    this.number = 00000;
    this.balance = 0;
}

public study3(String iD, int number, int balance) {
    ID = iD;
    this.number = number;
    this.balance = balance;
}

public int deposit(int a) {
    return balance += a;
}

public int withdraw(int a) {
    return balance -= a;
}

public void getbalance() {
    System.out.println("姓名："+ID+"\t账号："+number+"\t余额:"+balance);
}

// public static study3 found(int number) {
//
// }

public static void main(String[] args) {
    study3 s1 = new study3("王先生",23244,200);
    s1.deposit(200);
    s1.getbalance();
    s1.withdraw(50);
    s1.getbalance();
    
    
}

}

可以使用map集合存储