实现和接口

Question

I tried looking up tutorials and videos and I understand what implementing does, although I'm a bit confused as to how one would implement a class from the Java Library. In my homework, I'm suppose to utilize the class, DataSet and make it so it accepts Comparable objects. The program is suppose to record the Min and Max values depending on the objects, in this case, I'm suppose to use strings. I wasn't sure if I needed any classes to implement the Comparable interface, so I made two classes just in case I was suppose to do so. My real question is how do I actually incorperate a String variable in the tester class to actually read and compare the object to another? thanks in advance.

public class Word implements Comparable
{
private String str;

public Word()
{
    str = null;
}

public Word(String s)
{
    str = s;
}

 public int compareTo(Object other)
 {
    String n = (String) other;
    return str.compareTo(n);
 }

}

I wasn't sure which of the two classes would be suitable for implementing Although i think the String class below would not work at all b/c It's already a standard class so I wasn't too sure about using it

public class String implements Comparable
{
    public String s;

    public String()
    {
    s = null;
    }

public String(String str)
{
    s = str;
}
public int compareTo(Object other)
{
    String n = (String) other;
   return s.compareTo(n);
}
}


public interface Comparable
{
public int compareTo(Object other);
}


public class DataSet
{
 private Object maximum;
 private Object least;
 private Comparable compare;
 private int count;

 public DataSet(Comparable s)
 {
   compare = s;
 }

 public void add(Object x)
 {

   if(count == 0)
   least = x;
   if(count == 0 || compare.compareTo(x) >=0)
   maximum = x;
   else if(compare.compareTo(x) <0)
   least = x;
   count++;

 }
 public Object getMaximum()
 {
  return maximum;
 }

 public Object getLeast()
 {
   return least;
 }

 }


public class DataSetTester
{
   public static void main(String[] args)
  {
  Comparable n = new Word("sand");
  DataSet data = new DataSet(n);


  data.add(new Word(man));



  System.out.println("Maximum Word: " + data.getMaximum());
  System.out.println("Least Word: " + data.getLeast());
 }
}

Answer 1

An interface is a contract that showes that your class contain all methodes that are implemented in the interface. In this case the CompareTo(object other) . The String class already implements the comparable interface so you don't need youre own class. I think your data set class should look something like this :

public class DataSet<T implements Comparable>
{
 private T maximum;
 private T least;
 private T count;


 public void add(T x)
 {

   if(count == 0){
     least = x;
     maximum = x;
   }
   else if(least.compareTo(x) > 0)
     least = x;
   else if(maximum.compareTo(x) < 0)
     maximum = x;
   count++;
 }

 public T getMaximum()
 {
  return maximum;
 }

 public T getLeast()
 {
   return least;
 }

 }

T is a generic type and in your case it should be String, Here is how you create a new Data set: DataSet<String> ds = new DataSet<String>;