Java Successfully De-rusted

src/ArrayPractice.java

@@ -1,17 +1,37 @@
+import java.util.Arrays;
+
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
+    String[] stringList = new String[4];
+    System.out.println(Arrays.toString(stringList));
 
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+    stringList[0] = "hi";
+    stringList[1] = "hello";
+    stringList[2] = "howdy";
+    stringList[3] = "hey";
+    System.out.println(Arrays.toString(stringList));
 
     // Get the value of the array at index 2
+    String element2 = stringList[2];
+    System.out.println("Element at index 2: " + element2);
 
     // Get the length of the array
+    int stringListLength = stringList.length;
+    System.out.println("Length: " + stringListLength); 
 
     // Iterate over the array using a traditional for loop and print out each item
-
+    System.out.println("--- Traditional For Loop ---");
+    for (int i = 0; i < stringList.length; i++){
+      System.out.println(stringList[i]);
+    }
     // Iterate over the array using a for-each loop and print out each item
+    System.out.println("--- For Each Loop ---");
+    for (String string : stringList){
+      System.out.println(string);
+    }
 
     /*
      * Reminder!

src/ListPractice.java

@@ -1,27 +1,52 @@
+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> stringList = new ArrayList<String>();
+    System.out.println(stringList);
 
     // Add 3 elements to the list (OK to do one-by-one)
+    stringList.add("hello");
+    stringList.add("world");
+    stringList.add("!");
+    System.out.println(stringList);
 
     // Print the element at index 1
+    System.out.println(stringList.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)
+    stringList.set(1, "you");
+    System.out.println(stringList);
 
     // Insert a new element at index 0 (the length of the list will change)
+    stringList.add(0, "why");
+    System.out.println(stringList);
 
     // Check whether the list contains a certain string
+    System.out.println("Does the list contain \"hello\"? " + stringList.contains("hello"));
+    System.out.println("Does the list contain \".\"? " + stringList.contains("."));
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for (int i = 0; i < stringList.size(); i++) {
+      System.out.println("Index: " + i + " Value: " + stringList.get(i));
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(stringList);
+    System.out.println(stringList);
 
     // Iterate over the list using a for-each loop
-    // Print each value on a second line
+    // Print each value on a second line --a seperate line?
+    for (String string : stringList) {
+      System.out.println(string);
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,29 +1,58 @@
-
+import java.util.HashMap;
+import java.util.Map;
 
 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>();
+    System.out.println(myMap);
+
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    myMap.put("i", 56);
+    myMap.put("me", 23);
+    myMap.put("mine", 99);
+    System.out.println(myMap);
 
     // Get the value associated with a given key in the Map
+    System.out.println(myMap.get("me"));
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println("size: " + myMap.size());
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+    myMap.replace("mine", 2);
+    System.out.println(myMap);
 
     // Check whether the Map contains a given key
+    System.out.println("Contains \"you\"? " + myMap.containsKey("you"));
+    System.out.println("Contains \"me\"? " + myMap.containsKey("me"));
 
     // Check whether the Map contains a given value
+    System.out.println("Contains \"1\"? " + myMap.containsValue(1));
+    System.out.println("Contains \"2\"? " + myMap.containsValue(2));
 
     // Iterate over the keys of the Map, printing each key
+    System.out.println("--- Keys ---");
+    for (String key : myMap.keySet()){
+      System.out.println(key);
+    }
+    System.out.println();
 
     // Iterate over the values of the map, printing each value
+    System.out.println("--- Values ---");
+    for (int val : myMap.values()){
+      System.out.println(val);
+    }
+    System.out.println();
 
     // Iterate over the entries in the map, printing each key and value
-
+    System.out.println("--- Sets ---");
+    for (String key : myMap.keySet()){
+      System.out.println(key + " - " + myMap.get(key));
+    }
     /*
      * Usage tip!
      * 

src/NumberPractice.java

@@ -1,17 +1,31 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
+    float negFloat = -10;
+    System.out.println("Negative Float: " + negFloat);
 
     // Create an int with a positive value and assign it to a variable
+    int posInt = 10;
+    System.out.println("Positive Int: " + posInt);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    int remainder = posInt % 3;
+    System.out.println("Remainder: " + 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.
+    if (posInt % 2 != 0){
+      System.out.println("Odd");
+    }
+    else System.out.println("Even");
+
 
     // Divide the number by another number using integer division
+    int divided = posInt / 7;
+    System.out.println(posInt + " / 7 = " + divided );
+
 
     /*
      * Reminder!

src/Person.java

@@ -5,15 +5,24 @@
 
 public class Person {
   // Declare a public String instance variable for the name of the person
+  public String name;
+
   // Declare a private int instance variable for the age of the person
+  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
-
+  public String toString(){
+    return name + " - " + 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 me = new Person("Augy", 22);
+
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person sister = new Person("Alyssa", 16);
+
 
     // Print the first person
+    System.out.println(me);
 
     // Print the second person
+    System.out.println(sister);
 
     // Get the name of the first person and store it in a local variable
+    String firstPersonName = me.name;
+    System.out.println(firstPersonName);
 
     // 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 firstBirthYear = me.birthYear(2025);
+
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(firstBirthYear);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,18 +1,34 @@
+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> stringSet = new HashSet<String>();
+    System.out.println(stringSet);
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    stringSet.add("ahh");
+    stringSet.add("ahhhhh");
+    stringSet.add("ahhhhhhhhhhhhh");
+    System.out.println(stringSet);
 
     // Check whether the Set contains a given String
+    System.out.println("contains \"ah\"? " + stringSet.contains("ah"));
+    System.out.println("contains \"ahh\"? " + stringSet.contains("ahh"));
 
     // Remove an element from the Set
+    stringSet.remove("ahh");
+    System.out.println(stringSet);
 
     // Get the size of the Set
+    System.out.println("size: " + stringSet.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
-
+    for (String element : stringSet){
+      System.out.println(element);
+    }
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,25 +1,52 @@
+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 myString = "bagels";
+    System.out.println(myString);
 
     // Find the length of the string
+    int myStringLength = myString.length();
+    System.out.println("length: " + myStringLength);
 
     // Concatenate (add) two strings together and reassign the result
+    myString = myString + myString;
+    System.out.println("new string: " + myString);
 
     // Find the value of the character at index 3
+    char value3 = myString.charAt(3);
+    System.out.println("value at index 3: " + value3);
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    System.out.println("contains \"abc\"? " + myString.contains("abc"));
+    System.out.println("contains \"age\"? " + myString.contains("age"));
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < myString.length(); i++) {
+      System.out.println(i + ". " + myString.charAt(i));
+    }
 
     // Create an ArrayList of Strings and assign it to a variable
+    ArrayList<String> stringList= new ArrayList<String>();
+    System.out.println(stringList);
 
     // Add multiple strings to the List (OK to do one-by-one)
+    stringList.add("lipitytoo");
+    stringList.add("lipitytah");
+    stringList.add("lippytappy");
+    stringList.add("tootah");
+    System.out.println(stringList);
 
     // 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 conglomString = String.join(",", stringList);
+    System.out.println(conglomString);
+
 
     // Check whether two strings are equal
+    System.out.println("Are \"this\" and \"that\" equal? " + "this".equals("that"));
+    System.out.println("Is \"this\" and \"this\" equal? " + "this".equals("this"));
 
     /*
      * Reminder!

toRefresh.md

@@ -2,4 +2,9 @@
 
 As you work through this exercise, write down anything that you needed to look up or struggled to remember here. It can be just a word or two (e.g. "joining strings"). You can use this as a guide of what to make extra sure you're refreshed on before exams and interviews.
 
-- 
+- ArrayList.set
+- ArrayList methods in general
+- Using Collections Library
+- Printing content in array (toString)
+- String methods
+- overriding toString