Logical error ?

[Aristo]

Hello guys,
I'm wrote 2 classes Student & ArrayStudent class program that determines the average, youngest and oldest age in an array....the average and oldest works fine, but the youngest keeps on giving wrong output in the ArrayStudent class, no matter what I try....Please can anybody help and tell me what I'm doing wrong?
thanks for your anticipated help.

// Fig. 1.3: Student.java
// Student class definition
public class Student
{
	// A student's personal details
	private String name;
	private int age;

	// Student constructor initialises each instance variable
	public Student(String nameIn, int ageIn)
	{
		name = nameIn;
		age = ageIn;
	}

	// Return a student's name
	public String getName() {  return name; }

    // Return a student's age
    public int getAge()  { return age; }
}// end of class Student

// Fig. 1.3: ArrayStudent.java
// Application Class ArrayStudent is a testbed for class Student


import java.io.*;
public class ArrayStudent
{
    // keyboard input
    static BufferedReader keyboard = new BufferedReader(
                                     new InputStreamReader(System.in));

    public static void main(String args[] )throws IOException
    {
        String name;
        int age, number;
        System.out.print("How many students? ");
        number = Integer.parseInt(keyboard.readLine());
        Student s[] = new Student[number];
        // input into the array
        for(int index = 0; index < number; index++)
        {
          System.out.println();
          System.out.print("Enter Name of student number " + (index+1) + "? ");
          name = keyboard.readLine();
          System.out.print("Enter Age for " + name + "? ");
          age = Integer.parseInt(keyboard.readLine());
          s[index] = new Student(name,age);
        }
        printArray(s);  
        
    }// end of main
    
    // Prints elements of array - "Student objects"
    private static void printArray(Student s[])
    {
        System.out.println("Student List:");
        for(int index = 0; index < s.length; index++)
        {
          System.out.println(s[index].getName() + " " + s[index].getAge());
        }
        System.out.println("The total average age is " + findAverage(s));
        System.out.println("The youngest age is " + youngestAge(s));
        System.out.println("The oldest age is " + oldestAge(s));
    }// end of method printArray
    
    // Finding the average age.
    private static double findAverage(Student s[])
    {
        double sum = 0.0;
        for(int i = 0; i < s.length; i++)
        {
           sum += s[i].getAge();

        }
        return sum / s.length;        
    }
    
    //Finding the youngest age.
    private static int youngestAge(Student s[])
    {
        int youngest = 0;
        //youngest = s.[0];
        for(int i = 0; i < s.length; i++){
        
        if (s[i].getAge() < youngest){
            youngest = s[i].getAge();
        }
    }
        return youngest;
    }
    
    //Finding the oldest age.
    private static int oldestAge(Student s[])
    {
        int oldest = 0;
        for(int i = 0; i < s.length; i++){
        
        if (s[i].getAge() > oldest){
            oldest = s[i].getAge();
        }
    }
        return oldest;
    }
}// end of class ArrayStudent

[Aristo]

Hey...have been able to crack it :-)

int youngest = Integer.MAX_VALUE;

[Uladzimir]

Hi!

Please take a look carefully at youngestAge method. You set initial value of youngest eaquals to zero and after this you are making an iteration over the students. But NON of they has age less then 0.

Solution:
replace int oldest = 0;
with int oldest = 1000;

[nspils]

A rule of thumb which Uladzimir was applying: when you initialize a comparison (ordering) value which will be evaluated and reset by your program (oldest, youngest, widest, first, last, etc.), initialize with the last valid value in the "opposite" extreme. If you are initializing "youngest", set it to the highest possible valid age (150?), when "oldest", use lowest possible age (0?) - then, the first time you do an evaluation with one of your subjects, you for sure will set the value to a valid and "real" value.

[Aristo]

Well another solution could be....

int youngest = s[i].getAge();

But thanks anyway...