Simple java intro test

demo.java

import javax.crypto.IllegalBlockSizeException;

class Main {

  // Normally each class should be in a separate file.
  static class Student {
    private String name;

    public Student(String name){
      this.name = name;
    }

    public String getName(){
      return name;
    }
  }

  // Simple function taking a student
  public static void someFunction(Student a){
    System.out.println(" a:stud " + a.getName());
  }
  
  // Simple function throwing an exception
  public static void someFunctionBroken(Student a) throws IllegalBlockSizeException {

    if (a.getName().length() == 3){
      throw new IllegalBlockSizeException("Broken");
    }

    System.out.println(" b:stud " + a.getName());
  }

  // Main method called on program start (i.e., execution entry point for Main class)
  public static void main(String[] args) {
    Student s1 = new Student("Adam");
    Student s2 = new Student("Eve"); 
    
    System.out.println("Hello " + s1.getName() + " and " + s2.getName());

    // Task 1:
    // Add age field to the student, correct next 2 prints to print student UCO as integer.
    System.out.println(String.format("Name1: %10s, uco: %6d", s1.getName(), 123));
    System.out.println(String.format("Name2: %10s, uco: %6d\n", s2.getName(), 456));
    someFunction(s1);
    someFunction(s2);

    // Simple try-catch for exceptions
    try {
      someFunctionBroken(s1);
      someFunctionBroken(s2);
      System.out.println("Never printed out...");
    } catch(IllegalBlockSizeException e){
      System.out.println("IllegalBlockSizeException: " + e);
    } catch(Exception e){
      System.out.println("General Exception: " + e);
    }

    // Demo for formatting integer as hexa string
    System.out.println(String.format("\nHexa string: %02x", 32));

    // Task 2:
    byte[] arr = new byte[256];

    // Implement function which
    // Initializes the array with 0,1,2,3... and prints hexadecimally
    // the whole array (use for-loop).
    // Call the function on "arr"

    // Task 3: 
    // 3.1 Convert string "123" to integer
    // 3.2 Convert string "a123" to integer (use try-catch to prevent program crash, print error on exception)

    // Task 4:
    // 4.1 Get and print file size of arbitrary file on your file system with using class File, documentation: https://docs.oracle.com/javase/7/docs/api/java/io/File.html

    // (will need import the File class)
    // 4.2 Do the same for non-existent file, what happens? use try-catch, print error on exception
  }

}