Question

Now, we will write a Disk device, which is more specific than a generic device, and thus Disk should extend Device. Since we are extending the class, it will automatically inherit all of the functionality of the Device class. We will just add some specifics associated with disks - the notion of disk size, which should be stored as a long because disk sizes can be relatively large.

Something to think about: since we are not defining enabled() or disabled() here, what should happen if we try to call them for some Disk object?

The class should implement the following public methods:

• public Disk(String name, int id, long size) Initialize the device with the given name, ID, and now disk size. Be sure to use the parent class's constructor for part of this, because it's the only way you'll be able to initialize the parent's fields.
• @Override public String getCategory() This should return the value "disk"
• public long getSize() Retrieves the size of the disk in bytes.
• @Override public String toString() Returns the same result as the Device's version of toString() with the addition of the size in bytes in parenthesis. So for example, :disk 1, 7500rpm HDD (1099511627776 bytes)

Answer 1

Disk Class:

Code Image:

Code to Copy:

//Disk.java

public class Disk extends Device {

     //additional attribute

    private long size;

  

    //Implementation of Constructor

    public Disk(String name, int id, long size) {

    //passing name and id to super class

       super(name, id);

       this.size = size;

    }

    @Override

    //Implementation of getCategory method

    public String getCategory() {

    //return value should be disk

    return "disk";

    }

    //Implementation of getSize method

    public long getSize() {

    //return the retrieves size of

    //the disk in bytes

    return size;

    }      

    @Override

    //Implementation of toString method

    public String toString() {

    //addition of the size of the bytes

    //in parenthesis.

       return super.toString()+" ("+size+" bytes)";

    }

}

Complete Program:

Code Image:

Sample Output:

• I have tested the complete code with E4tester.java.

Code to Copy:

//Disk.java

public class Disk extends Device {

     //additional attribute

    private long size;

  

    //Implementation of Constructor

    public Disk(String name, int id, long size) {

    //passing name and id to super class

       super(name, id);

       this.size = size;

    }

    @Override

    //Implementation of getCategory method

    public String getCategory() {

    //return value should be disk

    return "disk";

    }

    //Implementation of getSize method

    public long getSize() {

    //return the retrieves size of

    //the disk in bytes

    return size;

    }      

    @Override

    //Implementation of toString method

    public String toString() {

    //addition of the size of the bytes

    //in parenthesis.

       return super.toString()+" ("+size+" bytes)";

    }

}

//Device.java

public class Device {

     // attributes

    private String name;

    private int id;

    private boolean enabled;

    // Implementation of Device Constructor

    //which is initialize fields

    public Device(String name, int id) {

    this.name = name;

        this.id = id;

        // by default it is disabled state

        enabled = false;

    }

    // Implementation of getName method

    //which returns name

    public final String getName() {

    return name;

    }

    //Implementation of getID method

    //which returns id

    public final int getID(){

    return id;

    }

    // Implementation of getCategory

    //which returns the category,

    public String getCategory() {

    //return generic

    return "generic";

    }

    // Implementation of enable method

    //which enables the device

    public void enable() {

    enabled = true;

    }

    //Implementation of disable method

    //which disables the device

    public void disable() {

    enabled = false;

    }

    //Implementation of isEnabled method

    //which returns the state of device

    public boolean isEnabled() {

    return enabled;

    }

    @Override

    //Implementation of toString() method

    public String toString() {

    return getCategory() + " " + id + ", " + name;

    }        

}

//Printer.java

public class Printer extends Device {

    

    private int numJobs;

    // Implementation of constructor

    public Printer(String name, int id) {

    // passing name and id to super class

        super(name, id);

        // initializing numJobs to 0

        numJobs = 0;

   }

    @Override

    //Implementation of getCategory method

    public String getCategory() {

    //the return value is printer

    return "printer";

    }

    @Override

    //Implementation of disable method

    public void disable() {

    // call disable method

    //which disabling the device

        super.disable();

        // resetting number of jobs

        numJobs = 0;

    }

    // Implementation of submitJob method

    //which submit a job

    public void submitJob() {

    // incrementing numJobs by 1

    //if device is enabled

        if (isEnabled()) {

        numJobs = numJobs +1 ;

        }

    }

    // Implementation of numJobs method

    //which returns the number of jobs

    public int numJobs() {

    //return numJobs

    return numJobs;

    }

    //Implementation of completeJob

    //which decrements the number of jobs

    public void completeJob() {

    if (numJobs > 0) {

          //decrement the numJobs

          numJobs = numJobs -1;

        }

    }

}