Java Derusting

src/ArrayPractice.java

@@ -1,22 +1,43 @@
-public class ArrayPractice {
-  public static void main(String[] args) {
+public class ArrayPractice 
+{
+  public static void main(String[] args) 
+  {
     // Create an array of Strings of size 4
+    String arrayItems[] = {"One", "Two",  "Three", "Four"};
+    System.out.println(arrayItems[0]  + " " + arrayItems[1] + " " + arrayItems[2] + " " + arrayItems[3]);
 
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+    arrayItems[0] = "Java";
+    arrayItems[1] = "C++";
+    arrayItems[2] = "C#";
+    arrayItems[3] = "Python";
+
+    System.out.println(arrayItems[0] + " " + arrayItems[1] + " " + arrayItems[2] + " " + arrayItems[3]);
 
     // Get the value of the array at index 2
+    System.out.println(arrayItems[2]);
 
     // Get the length of the array
+    System.out.println(arrayItems.length);
 
     // Iterate over the array using a traditional for loop and print out each item
+    for (int i = 0; i < arrayItems.length; i++) 
+    {
+          System.out.println(arrayItems[i]);
+    }
 
     // Iterate over the array using a for-each loop and print out each item
+    for (String items : arrayItems) 
+    {
+          System.out.println(items);
+    }
 
     /*
      * Reminder!
      * 
      * Arrays start at index 0
      */
   }
+
 }

src/ListPractice.java

@@ -1,27 +1,60 @@
-public class ListPractice {
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Collections;
 
+public class ListPractice 
+{
 
-  public static void main(String[] args) {
-    // Create an empty ArrayList of Strings and assign it to a variable of type List
 
+  public static void main(String[] args) 
+  {
+    // Create an empty ArrayList of Strings and assign it to a variable of type List
+    List<String> listContainer = new ArrayList<String>();
+    System.out.println(listContainer);
+
     // Add 3 elements to the list (OK to do one-by-one)
+    listContainer.add("One");
+    listContainer.add("Two");
+    listContainer.add("Three");
+    System.out.println(listContainer);
 
     // Print the element at index 1
+    System.out.println(listContainer.get(1));
 
     // Replace the element at index 1 with a new value
     // (Do not insert a new value. The length of the list should not change)
+    listContainer.set(1, "New");
+    System.out.println(listContainer);
 
     // Insert a new element at index 0 (the length of the list will change)
+    listContainer.addFirst("Sky");
+    System.out.println(listContainer);
 
     // Check whether the list contains a certain string
+    System.out.println(listContainer.contains("New"));
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for (int i = 0; i < listContainer.size(); i++) 
+    {
+          System.out.println("Index: " + listContainer.indexOf(listContainer.get(i)) + " & Value: " + listContainer.get(i));
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(listContainer);
+    System.out.println(listContainer);
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    String listItems = "";
+
+    for (Object item : listContainer) 
+    {
+          System.out.println(item);
+          listItems += (item + " ");
+    }
+
+    System.out.println(listItems);
 
     /*
      * Usage tip!
@@ -33,4 +66,5 @@ public static void main(String[] args) {
      * index values a for-each loop is cleaner.
      */
   }
+
 }

src/MapPractice.java

@@ -1,28 +1,56 @@
+import java.util.HashMap;
+import java.util.Map;
 
-
-public class MapPractice {
-  public static void main(String[] args) {
+public class MapPractice 
+{
+  public static void main(String[] args) 
+  {
     // Create a HashMap with String keys and Integer values and
     // assign it to a variable of type Map
+    Map<String, Integer> mapPractice = new HashMap<String, Integer>();
+    System.out.println(mapPractice);
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    mapPractice.put("Java", 27);
+    mapPractice.put("C", 11);
+    mapPractice.put("Python", 120);
+
+    System.out.println(mapPractice);
 
     // Get the value associated with a given key in the Map
+    System.out.println(mapPractice.get("C"));
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(mapPractice.size());
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+    mapPractice.put("Python", 2);
+    System.out.println(mapPractice);
 
     // Check whether the Map contains a given key
+    System.out.println(mapPractice.containsKey("Java"));
 
     // Check whether the Map contains a given value
+    System.out.println(mapPractice.containsValue(27));
 
     // Iterate over the keys of the Map, printing each key
+    for (String keys : mapPractice.keySet()) 
+    {
+          System.out.println(keys);
+    }
 
     // Iterate over the values of the map, printing each value
+    for (int values : mapPractice.values()) 
+    {
+          System.out.println(values);
+    }
 
     // Iterate over the entries in the map, printing each key and value
+    for (String keys : mapPractice.keySet()) 
+    {
+          System.out.println(keys + " and " + mapPractice.get(keys));
+    }
 
     /*
      * Usage tip!
@@ -40,4 +68,5 @@ public static void main(String[] args) {
      * and you don't care about any ordering.
      */
   }
+
 }

src/NumberPractice.java

@@ -1,17 +1,33 @@
-public class NumberPractice {
-  public static void main(String args[]) {
+public class NumberPractice 
+{
+  public static void main(String args[]) 
+  {
     // Create a float with a negative value and assign it to a variable
+    float negNum = -5.666f;
+    System.out.println(negNum);
 
     // Create an int with a positive value and assign it to a variable
+    int posNum = 7;
+    System.out.println(posNum);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    System.out.println(posNum % 3);
 
     // Use the modulo % operator to determine whether the number is even
     // (A number is even if it has a remainder of zero when divided by 2)
     // Use an if-else to print "Even" if the number is even and "Odd"
     // if the number is odd.
+    if (posNum % 2 == 0) 
+    {
+          System.out.println("Even");
+    }
+    else
+    {
+          System.out.println("Odd");
+    }
 
     // Divide the number by another number using integer division
+    System.out.println(posNum / 2);
 
     /*
      * Reminder!
@@ -22,4 +38,5 @@ public static void main(String args[]) {
      */
 
   }
+
 }

src/Person.java

@@ -3,16 +3,29 @@
  * the Person class.
  */
 
-public class Person {
+public class Person 
+{
   // Declare a public String instance variable for the name of the person
   // Declare a private int instance variable for the age of the person
+  public String name;
+  private int age;
 
 
   // Create a constructor that takes the name and age of the person
   // and assigns it to the instance variables
+  public Person(String name, int age)
+  {
+     this.name = name;
+     this.age  = age;
+  }
 
 
   // Create a toString method that gives the name and age of the person
+  @Override
+  public String toString() 
+  {
+     return name + ": " + age;
+  }
 
 
   // Implement the below public instance method "birthYear"
@@ -29,24 +42,39 @@ public class Person {
    */
   // (create the instance method here)
 
+  public int birthyear(int currentYear)
+  {
+     return currentYear - age;
+  }
 
-  public static void main(String[] args) {
+
+  public static void main(String[] args) 
+  {
     // Create an instance of Person
+    Person personOne = new Person("Clair", 32);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person personTwo = new Person("Jill", 35);
 
     // Print the first person
+    System.out.println(personOne.toString());
 
     // Print the second person
+    System.out.println(personTwo.toString());
 
     // Get the name of the first person and store it in a local variable
+    String personName = personOne.name;
+    System.out.println(personName);
 
     // Using the birthYear method, get the birth year of the first person
     // and store it in a local variable. Input the actual current year (e.g. 2025)
     // as the argument.
+    int born = personOne.birthyear(2025);
+    System.out.println(born);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(personOne.age);
 
     /**
      * Terminology!
@@ -63,4 +91,5 @@ public static void main(String[] args) {
      * Each instance has its own instance variables: Auberon's age can be different from Baya's age.
      */
   }
+
 }

src/SetPractice.java

@@ -1,17 +1,37 @@
-public class SetPractice {
-  public static void main(String[] args) {
+import java.util.HashSet;
+import java.util.Set;
+
+public class SetPractice 
+{
+  public static void main(String[] args) 
+  {
     // Create a HashSet of Strings and assign it to a variable of type Set
+    Set<String> hashItems =  new HashSet<String>();
+    System.out.println(hashItems);
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    hashItems.add("One");
+    hashItems.add("Two");
+    hashItems.add("Three");
+
+    System.out.println(hashItems);
 
     // Check whether the Set contains a given String
+    System.out.println(hashItems.contains("Two"));
 
     // Remove an element from the Set
+    hashItems.remove("Two");
+    System.out.println(hashItems);
 
     // Get the size of the Set
+    System.out.println(hashItems.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
+    for (String items : hashItems) 
+    {
+          System.out.println(items);
+    }
 
     /*
      * Warning!
@@ -26,4 +46,5 @@ public static void main(String[] args) {
      * Also remember that sets do NOT have duplicates.
      */
   }
+
 }