Question

I’m trying to write a program that accepts type comparable into the DataSet class so it can find the maximum and minimum values. The only problem is that I can’t compile either one and I’m a little confused by how to fix the errors. Thanks

DataSet.java:

public class DataSet<T implements Comparable>
{

 private T maximum;
 private T least;
 private int 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;
 }

}

error:

java:5: error: '(' or '[' expected
        DataSet<String> ds = new DataSet<String>;
                                                ^
1 error

Comparable:

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

no errors here

public class DataSetTester
{
public static void main(String[] args)
{
    DataSet<String> ds = new DataSet<String>;
    ds.add(man);
    ds.add(woman);
    System.out.println("Maximum Word: " + ds.getMaximum());

 }
}

error:

java:5: error: '(' or '[' expected
        DataSet<String> ds = new DataSet<String>;
                                                ^

Answer 1

Watch out for the missing parantesis:

DataSet<String> ds = new DataSet<String>();

Also, you are misuing the “implements” keyword. For generics, you should use the extends keyword. Therefore, it should read:

public class DataSet<T extends Comparable<T>>

You are also missing the “” when passing the string arguments:

DataSet<String> ds = new DataSet<String>();
ds.add("man");
ds.add("woman");

Most of these errors are pretty trivial, you should try practicing a bit more to understand the language. Also, the error messages from the compiler should help.