Thread: Sorting substring?

Here is my code:

import java.util.Arrays;
 
import javax.swing.*;
 
public class childNameAge {
	public static void main(String[] args) {
		int numberOfChildren;
		String indata;
 
		indata = JOptionPane.showInputDialog(null, "How many children do you want to register?");
		numberOfChildren = Integer.parseInt(indata);
 
		String[] nameOfChild = new String[numberOfChildren + 1];
 
		for (int i = 1; i <= numberOfChildren; i++) {
			nameOfChild[i] = JOptionPane.showInputDialog(null, "Personal numer and name " + i + "\nFormat: num-name");
		}
		for (int i = 1; i <= numberOfChildren; i++) {
			System.out.println(nameOfChild[i]);
		}
		System.out.println("Picking out year of birth...");
		for(int i=1; i<=numberOfChildren; i++){
 
		System.out.println(Integer.parseInt(nameOfChild[i].substring(0, 2)));
		}
	}
}

Now I want to sort the array, the biggest number last och and the smallest first. Then I want to connect the age to the right name again and print out childrens year of birth and name.

I'm guessing that what you're doing is building a *map* of child-name -> year of birth, right? No, that's not right, you've got id numbers in there - is that because two children may have the same name? So the map is id -> (name, yob) where 'yob' is year-of-birth, right? You can 'connect' the name to the yob by making a class 'ChildYOB' (for example) with two data members: a name and a year.

You could read in all your values, and *put* each id->ChildYOB in a java.util.TreeMap. TreeMap arranges its keys in 'natural order', so for integers that's small-to-large, but it has methods starting "descending..." which would give you large-to-small. When you retrieve ChildYOB values from the TreeMap, the names would be already 'connected' to year of birth because the pair would be encapsulated by the class you've written.

That sounds like a lot of work but the classes in the Java API - once you get to know them - make programming something like this very easy, requiring very few lines of code. If you were to try to do this without using the Java API by using arrays of primitive types, you'd end up with a much larger, much harder to understand and debug program.