derustingfork

README.md

@@ -1,4 +1,4 @@
-# DO NOT DOWNLOAD THIS CODE AS A ZIP FILE
+# DO NOT DOWNLOAD THIS CODE AS A ZIP FILE.
 # READ ME FIRST BEFORE DOWNLOADING
 
 This repository will be used to practice both your git and Java skills. DO NOT DOWNLOAD IT AS A ZIP FILE. Downloading it as a zip file will prevent the git commands from working properly.

src/ArrayPractice.java

@@ -1,17 +1,40 @@
+import java.util.Arrays;
+
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
+    String[] myArray = new String[4];
+    System.out.println(myArray.toString());
 
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+    /*for (int i = 0; i < myArray.length; i++)
+    {
+      myArray[i] = "index" + i;
+    }*/
+    myArray[0] = "index0";
+    myArray[1] = "index1";
+    myArray[2] = "index2";
+    myArray[3] = "index3";
+    System.out.println(Arrays.toString(myArray));
 
     // Get the value of the array at index 2
+    System.out.println(myArray[2]);
 
     // Get the length of the array
+    System.out.println(myArray.length);
 
     // Iterate over the array using a traditional for loop and print out each item
+    for (int i = 0; i < myArray.length; i++)
+    {
+      System.out.println("for-loop: " + myArray[i]);
+    }
 
     // Iterate over the array using a for-each loop and print out each item
+    for (String item : myArray)
+    {
+      System.out.println("for-each loop: " + item);
+    }
 
     /*
      * Reminder!

src/ListPractice.java

@@ -1,27 +1,54 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 public class ListPractice {
 
 
   public static void main(String[] args) {
     // Create an empty ArrayList of Strings and assign it to a variable of type List
+    List<String> list = new ArrayList<String>();
 
     // Add 3 elements to the list (OK to do one-by-one)
+    list.add("i0");
+    list.add("i1");
+    list.add("i2");
 
     // Print the element at index 1
+    System.out.println(list.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)
+    list.set(1, "replaced");
+    System.out.println(list);
 
     // Insert a new element at index 0 (the length of the list will change)
+    list.add(0, "insertNew");
+    System.out.println(list);
 
     // Check whether the list contains a certain string
+    if (list.contains("insertNew"))
+    {
+      System.out.println("insertNew exists in list.");
+    }
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for (int i=0; i < list.size(); i++)
+    {
+      System.out.println("Index: : " + i + ", Value: " + list.get(i).toString());
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(list);
+    System.out.println(list);
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    for (String item : list)
+    {
+      System.out.println("for-each loop: " + item + "\n");
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,28 +1,66 @@
-
+import java.util.Map;
+import java.util.HashMap;
 
 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> myMap = new HashMap<String, Integer>();
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    myMap.put("item_0", 0);
+    myMap.put("item_1", 1);
+    myMap.put("item_2", 2);
+    System.out.println(myMap);
 
     // Get the value associated with a given key in the Map
+    System.out.println(myMap.get("item_1"));
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(myMap.size());
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+    myMap.put("item_1", 99);
+    System.out.println(myMap);
 
     // Check whether the Map contains a given key
+    if (myMap.containsKey("item_7"))
+    {
+      System.out.println(true);
+    }
+    else
+    {
+      System.out.println(false);
+    }
 
     // Check whether the Map contains a given value
+    if (myMap.containsValue(99))
+    {
+      System.out.println(true);
+    }
+    else
+    {
+      System.out.println(false);
+    }
 
     // Iterate over the keys of the Map, printing each key
+    for (String key : myMap.keySet())
+    {
+      System.out.println("for-each key: " + key);
+    }
 
     // Iterate over the values of the map, printing each value
+    for (Integer value : myMap.values())
+    {
+      System.out.println("for-each value: " + value);
+    }
 
     // Iterate over the entries in the map, printing each key and value
+    for (String keyEntry : myMap.keySet())
+    {
+      System.out.println("Key: " + keyEntry + " & the value: " + myMap.get(keyEntry));
+    }
 
     /*
      * Usage tip!

src/NumberPractice.java

@@ -1,17 +1,34 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
+    float num = -3.44f;
+    System.out.println(num);
 
     // Create an int with a positive value and assign it to a variable
+    int x = 2;
+    System.out.println(x);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    int remainder = 7%3;
+    System.out.println(remainder);
 
     // 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.
+    int numEorO = 3;
+    if (numEorO % 2 == 0)
+    {
+      System.out.println("This number is even: " + numEorO);
+    }
+    else
+    {
+      System.out.println("This number is odd: " + numEorO);
+    }
 
     // Divide the number by another number using integer division
+    int result = numEorO/x;
+    System.out.println("int division result: " + result);
 
     /*
      * Reminder!

src/Person.java

@@ -3,17 +3,26 @@
  * 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 n, int a)
+  {
+    name = n;
+    age = a;
+  }
 
 
   // Create a toString method that gives the name and age of the person
-
+  public String toString()
+  {
+    return "Name: " + name.toString() + ", Age: " + String.valueOf(age);
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -28,25 +37,37 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
+  public int birthYear(int currentYear)
+  {
+    return currentYear-age;
+  }
 
 
   public static void main(String[] args) {
     // Create an instance of Person
+    Person john = new Person("John", 25);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person mark = new Person("Mark", 30);
 
     // Print the first person
+    System.out.println(john.toString());
 
     // Print the second person
+    System.out.println(mark.toString());
 
     // Get the name of the first person and store it in a local variable
+    String johnsName = john.name;
+    System.out.println(johnsName);
 
     // 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 johnsBirthYear = john.birthYear(2025);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(johnsBirthYear);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,44 @@
+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> mySet = new HashSet<String>();
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    for (int i=0; i<3; i++)
+    {
+      mySet.add("element" + i);
+    }
+    System.out.println(mySet);
 
     // Check whether the Set contains a given String
+    if (mySet.contains("element2"))
+    {
+      System.out.println(true);
+    }
+    else
+    {
+      System.out.println(false);
+    }
 
     // Remove an element from the Set
+    mySet.remove("element2");
+    System.out.println(mySet);
 
     // Get the size of the Set
+    System.out.println(mySet.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
+    String[] myArray = new String[2];
+    mySet.toArray(myArray);
+
+    for (int i=0; i<mySet.size(); i++)
+    {
+      System.out.println("Iteration: " + myArray[i]);
+    }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,25 +1,61 @@
+import java.util.List;
+import java.util.ArrayList;;
+
 public class StringPractice {
   public static void main(String[] args) {
     // Create a string with at least 5 characters and assign it to a variable
+    String word = "hello";
 
     // Find the length of the string
+    System.out.println(word.length());
 
     // Concatenate (add) two strings together and reassign the result
+    word = "NewWord";
+    System.out.println(word);
 
     // Find the value of the character at index 3
+    System.out.println(word.charAt(3));
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    if (word.contains("New"))
+    {
+      System.out.println(true);
+    }
+    else
+    {
+      System.out.println(false);
+    }
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < word.length(); i++)
+    {
+      System.out.println(word.charAt(i));
+    }
 
     // Create an ArrayList of Strings and assign it to a variable
+    List<String> myArray = new ArrayList<String>();
 
     // Add multiple strings to the List (OK to do one-by-one)
+    for (int i=0; i < 4; i++)
+    {
+      myArray.add("String" + i);
+    }
+    System.out.println(myArray);
 
     // Join all of the strings in the list together into a single string separated by commas
     // Use a built-in method to achieve this instead of using a loop
+    String singleString = String.join(",", myArray);
+    System.out.println(singleString);
 
     // Check whether two strings are equal
+    if (word.equals("NewWord"))
+    {
+      System.out.println(true);
+    }
+    else
+    {
+      System.out.println(false);
+    }
 
     /*
      * Reminder!