Arranging by Alphabetical Order

Question

I\'m new to Java and I\'m trying to arrange an arrayList of terms in alphabetical order. (A term is defined as a char and an int) (e.g. {Term(\'Z\',4),Term(\'C\',3),Term(\

Answer 1

Your problem with this line of Code. Your class is not a Type of Comparable So, On which property or criteria compareTo() method will compare these two objects ???

   res = maxtest.compareTo(maxtest2); //Your maxtest object is not Comparable Type.

You must need to make your class Term Comparable type. and , Override the method compareTo() as per your need.

You have not mentioning the variable's or structure of your class Term . So, I am assuming that your class have such kind of Structure .

public class Term implements Comparable {
    private Character alpha;
   private int number;
   //getter and setters +Constructors as you specified
   ....
    ....
     ...
      .....
//  Now Set a criteria to sort is the Alphanumeric.
    @Override
    public int compareTo(Term prm_obj) {
        if (prm_obj.getAlpha() > this.alpha) {
            return 1;
        } else if (prm_obj.getAlpha() < this.alpha) {
            return -1;

        } else {
            return 0;
        }

    }

Now Your Class become a comparable Type. So you may apply Collections.sort(Collection obj) which automatically sort your ArrayList.

Here I write a demo for this.

public static void main(String... args){

    List obj_listTerm = new ArrayList<>();
     //add all the data you given in question
    obj_listTerm .add(new Term('Z', 4)); 
    obj_listTerm .add(new Term('Q', 2));
    obj_listTerm .add(new Term('c', 3));

    // print without Sorting your Term ArrayList.
    System.out.println("This is the list unsorted: " + myTermList);
    // Sort Using Collections.sort() Method.

    Collections.sort(myTermList);

    // After applying sort() you may see your Sorted ArrayList.
    System.out.println("This is the list SORTED: " + myTermList);
}