Use a Comparator to Sort Accounts by Last Name

Here is a Java Program to Use a comparator to sort accounts by last name.

import java.util.*;

// Compare last whole words in two strings.
class TComp implements Comparator {
  public int compare(Object a, Object b) {
    int i, j, k;
    String aStr, bStr;

    aStr = (String) a;
    bStr = (String) b;

    // find index of beginning of last name
    i = aStr.lastIndexOf(' ');
    j = bStr.lastIndexOf(' ');

    k = aStr.substring(i).compareTo(bStr.substring(j));
    if(k==0) // last names match, check entire name
      return aStr.compareTo(bStr);
    else
      return k;
  }

  // no need to override equals
}

class TreeMapDemo2 {
  public static void main(String args[]) {
    // Create a tree map
    TreeMap tm = new TreeMap(new TComp());
    
    // Put elements to the map
    tm.put("John Doe", new Double(3434.34));
    tm.put("Tom Smith", new Double(123.22));
    tm.put("Jane Baker", new Double(1378.00));
    tm.put("Tod Hall", new Double(99.22));
    tm.put("Ralph Smith", new Double(-19.08));

    // Get a set of the entries
    Set set = tm.entrySet();

    // Get an iterator
    Iterator itr = set.iterator();

    // Display elements
    while(itr.hasNext()) {
      Map.Entry me = (Map.Entry)itr.next();
      System.out.print(me.getKey() + ": ");
      System.out.println(me.getValue());
    }
    System.out.println();

    // Deposit 1000 into John Doe's account
    double balance =  ((Double)tm.get("John Doe")).doubleValue();
    tm.put("John Doe", new Double(balance + 1000));
    System.out.println("John Doe's new balance: " +
      tm.get("John Doe"));
  }
}

Output of Above Java Program
Jane Baker: 1378.0
John Doe: 3434.34
Tod Hall: 99.22
Ralph Smith: -19.08
Tom Smith: 123.22

John Doe's new balance: 4434.34