You can simply create a new empty array and assign that:

doctors = new Doctor[size];

The array will be defined but the objects will not be created yet.

It depends on whether you want to make it a null reference, have size 0, or make all the values = null.

For an array, such as Doctor[], here are some alternatives - not sure which one is applicable for your circumstance...

// setting the array to null
doctors = null;

// removing all array entries, making an array of size 0
doctors = new Doctor[0];

// keeping the array the same size, but making all values = null
doctors = new Doctor[doctors.length];

If it's an array, you need to reinitialize it.

publiv void clear() {
    this.doctors = null;
}

list = null

or

list = new int[list.length];

public void clearArray(Object[] Array){
    if (Array==null){
        return;
    }
    for (Object ob: Array){
         ob=null;
    }
}