Java Derusting

src/ArrayPractice.java

@@ -1,18 +1,29 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
-
+    String arr[] = new String[4];
     // Set the value of the array at each index to be a different String
     // It's OK to do this one-by-one
+    arr[0] = "cake";
+    arr[1] = "cookies";
+    arr[2] = "pancake";
+    arr[3] = "cupcake";
 
     // Get the value of the array at index 2
-
+    System.out.println(arr[2]);
+    System.out.println();
     // Get the length of the array
-
+    System.out.println(arr.length);
+    System.out.println();
     // Iterate over the array using a traditional for loop and print out each item
-
+    for(int i = 0; i < arr.length; i++){
+      System.out.println(arr[i]);
+    }
+    System.out.println();
     // Iterate over the array using a for-each loop and print out each item
-
+    for(String dessert: arr){
+      System.out.println(dessert);
+    }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,41 @@
+import java.util.ArrayList;
+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
-
+    ArrayList<String> list = new ArrayList<>();
     // Add 3 elements to the list (OK to do one-by-one)
-
+    list.add("Cake");
+    list.add("Ice Cream");
+    list.add("Macaron");
     // Print the element at index 1
-
+    System.out.println(list.get(0));
     // 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,"Bingsu");
+    System.out.println(list.get(1)+ " " + list.size());
     // Insert a new element at index 0 (the length of the list will change)
-
+    list.add(0,"Cookies");
+    System.out.println(list+ " " + list.size());
     // Check whether the list contains a certain string
-
+    System.out.println(list.contains("Cake") );
+    System.out.println();
     // 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(list.get(i));
+    }
     // Sort the list using the Collections library
-
+    Collections.sort(list);
+    System.out.println();
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+    for(String dessert : list){
+      System.out.println(dessert);
+    }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,29 +1,48 @@
-
+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
-
+    HashMap<String, Integer> foods = new HashMap<>();
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
-
+    foods.put("hot dog", 1);
+    foods.put("sushi", 2);
+    foods.put("pizza", 3);
+    foods.put("cake", 4);
+    System.out.println();
     // Get the value associated with a given key in the Map
-
+    System.out.println(foods.get("sushi"));
+    System.out.println();
     // Find the size (number of key/value pairs) of the Map
-
+    System.out.println(foods.size());
+    System.out.println();
     // Replace the value associated with a given key (the size of the Map shoukld not change)
-
+    foods.put("hot dog", 2);
+    System.out.println(foods);
+    System.out.println();
     // Check whether the Map contains a given key
-
+    System.out.println(foods.containsKey("sushi"));
+    System.out.println();
     // Check whether the Map contains a given value
-
+    System.out.println(foods.containsValue(4));
+    System.out.println();
     // Iterate over the keys of the Map, printing each key
-
+    for(String food : foods.keySet()){
+      System.out.println(food);
+    }
+    System.out.println();
     // Iterate over the values of the map, printing each value
-
+    for(Integer food : foods.values()){
+      System.out.println(food);
+    }
+    System.out.println();
     // Iterate over the entries in the map, printing each key and value
-
+    for(Map.Entry<String, Integer> foodInventory : foods.entrySet()){
+      System.out.println(foodInventory);
+    }
     /*
      * Usage tip!
      * 

src/NumberPractice.java

@@ -1,18 +1,24 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
-
+    float negativeFloat = -2.0f;
     // Create an int with a positive value and assign it to a variable
-
+    int postiveValue = 4;
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+    System.out.println(postiveValue%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(postiveValue % 2 == 0){
+      System.out.println("even");
+    } else {
+      System.out.println("odd");
+    }
 
     // Divide the number by another number using integer division
-
+    System.out.println(postiveValue/3);
     /*
      * Reminder!
      * 

src/Person.java

@@ -6,14 +6,20 @@
 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 = "Jerry";
+  private int age = 1000;
   // 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"
   // There should NOT be any print statement in this method.
@@ -28,26 +34,32 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
-
+  public static int birthYear(int age){
+    return 2025 - age;
+  }
 
   public static void main(String[] args) {
     // Create an instance of Person
-
+    Person human = new Person("Timmy", 20);
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
-
+    Person human2 = new Person("Joe", 30);
     // Print the first person
-
+    System.out.println(human.toString());
+    System.out.println();
     // Print the second person
-
+    System.out.println(human2.toString());
+    System.out.println();
     // Get the name of the first person and store it in a local variable
-
+    String firstPersonsName = human.name;
+    System.out.println(firstPersonsName);
+    System.out.println();
     // 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 firstPersonsBirthYear = birthYear(human.age);
     // In a separate statement, print the local variable holding the birth year.
-
+    System.out.println(firstPersonsBirthYear);
     /**
      * Terminology!
      * 

src/SetPractice.java

@@ -1,18 +1,30 @@
+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> hashbrown = new HashSet<>();
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
-
+    hashbrown.add("potatoes");
+    hashbrown.add("flour");
+    hashbrown.add("egg");
+    System.out.println();
     // Check whether the Set contains a given String
-
+    System.out.println(hashbrown.contains("potatoes"));
+    System.out.println();
     // Remove an element from the Set
-
+    hashbrown.remove("flour");
+    System.out.println(hashbrown);
+    System.out.println();
     // Get the size of the Set
-
+    System.out.println(hashbrown.size());
+    System.out.println();
     // Iterate over the elements of the Set, printing each one on a separate line
-
+    for(String Ingredient : hashbrown){
+      System.out.println(Ingredient);
+    }
+    System.out.println();
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,26 +1,61 @@
+import java.util.Arrays;
+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 = "Chariot";
     // Find the length of the string
-
+    System.out.println(word.length());
+    System.out.println();
     // Concatenate (add) two strings together and reassign the result
-
+    String first = "Number";
+    String second = "Two";
+    String firstSecond = first+second;
+    System.out.println(firstSecond);
+    System.out.println();
     // Find the value of the character at index 3
-
+    System.out.println(word.charAt(3));
+    System.out.println();
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    String Alphabet = "abc";
+    String noABC = "s";
+    if (Alphabet.contains("abc")) {
+      System.out.println("Alphabet contains \"abc\"");
+    }
 
+    if (noABC.contains("abc")) {
+      System.out.println("Alphabet contains \"abc\"");
+    } else{
+      System.out.println("noABC does not contain \"abc\"");
+    }
+    System.out.println();
     // Iterate over the characters of the string, printing each one on a separate line
-
-    // Create an ArrayList of Strings and assign it to a variable
-
+    String dessert = "macaron";
+    for (int i = 0; i < dessert.length(); i++) {
+      System.out.println(dessert.charAt(i));
+    }
+    System.out.println();
+    // Create an ArrayList of Strings and assign it to a variable 
+    // ArrayList<String> recipe = new ArrayList<String>(Arrays.asList("cheese","sugar","flour","egg whites"));
+    ArrayList<String> recipe = new ArrayList<String>();
+    System.out.println();
     // Add multiple strings to the List (OK to do one-by-one)
-
+    recipe.add("cheese");
+    recipe.add("sugar");
+    recipe.add("flour");
+    recipe.add("egg whites");
+    System.out.println();
     // 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
-
+    ArrayList<String> recipeMixed = new ArrayList<String>(Arrays.asList("cheese","sugar","flour","egg whites"));
+    System.out.println(recipeMixed);
+    System.out.println();
     // Check whether two strings are equal
-
+    if(recipeMixed.get(0).equals(recipeMixed.get(1))){
+      System.out.println("Same ingredient");
+    }else{
+      System.out.println("Not the same");
+    }
     /*
      * Reminder!
      *