Code gives error supposed to compare pairs

Question

question is
Expand Pair.java by testing it with at least 4 more differing Pair combinations (both primitives & classes). Find (or write) at least one other set of Pair that you can compare without altering the comparePairs method.
public class Pair<K, V> {
  K key;
  V value;
  public void set(K k, V v) {
    key = k;
    value = v;
  public K getKey() { return key; }
  public V getValue() { return value; }
  public String toString() {
    return "[" + getKey() + ", " + getValue() + "]";
  // Comparing Pairs - Slide 34
  public static <K extends Comparable,V,L,W> int
      comparePairs(Pair<K,V> p, Pair<L,W> q) {
    return p.getKey().compareTo(q.getKey());
    // p's key MUST implement compareTo
  /* IMPORTANT: This is very flexible code BUT it does
   *            allow for compilation of Pair objects that
   *            are not compatible. Safer to use only K,V.
   *            Test it below!
  public static void main (String[] args) {
    Pair<String,Integer> pair1 = new  Pair<String,Integer>();
    pair1.set(new String("a"), new Integer(36));
    System.out.println(pair1);
    Pair<Student,Double> pair2 = new  Pair<Student,Double>();
    pair2.set(new Student("A5976","Sue",19), new Double(9.5));
    System.out.println(pair2);
    Pair<String,Integer> pair3 = new  Pair<String,Integer>();
    pair3.set(new String("b"), new Integer(63));
    System.out.println(pair3);
    ///this is what i have added
    Pair<String,Student> pair4 = new  Pair<String,Student>();
    pair4.set(new String("c"), new Student("A9874","Jack",20));
    System.out.println(pair4);
    Pair<Integer,Student> pair5 = new  Pair<Integer,Student>();
    pair5.set(new Integer(3), new Student("A9471","Bal",20));
    System.out.println(pair5);
    Pair<String,Student> pair6 = new  Pair<Integer,Double>();
    pair6.set(new Integer(7), new Double(4.5));
    System.out.println(pair6);
    Pair<String,Student> pair7 = new  Pair<Double,String>();
    pair7.set(new Double(6.9),(new String("g"));
    System.out.println(pair7);
    // The comparison will be of the "String" keys AND
    // String implements the Comparable interface
    System.out.println(comparePairs(pair1, pair7)); // works; displays -1 because a < b
    // System.out.println(comparePairs(pair2, pair1)); // doesn't work BUT
    // there will ONLY be a compiler error if <K extends Comparable, V> is used
    // in the comparePairs declaration.
}

Answer 1

885018 wrote:
--------------------Configuration: <Default>--------------------
java.lang.NoClassDefFoundError: Pair
Caused by: java.lang.ClassNotFoundException: Pair
     at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
     at java.security.AccessController.doPrivileged(Native Method)
     at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Could not find the main class: Pair. Program will exit.
Exception in thread "main"
Process completed.The code you posted doesn't compile at all. What happened when you ran javac?