Completed Derusting

src/ArrayPractice.java

@@ -2,17 +2,26 @@ public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
 
+    String[] myArray = 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
-
+    myArray[0] = "hi";
+    myArray[1] = "hello";
+    myArray[2] = "hey";
+    myArray[3] = "howdy";
     // 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(i + ": " + myArray[i]);
+    }
     // Iterate over the array using a for-each loop and print out each item
-
+    for(String string : myArray){
+      System.out.println(string);
+    }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,40 @@
+import java.util.*;
+
 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> myList = new ArrayList<String>();
     // Add 3 elements to the list (OK to do one-by-one)
-
+    myList.add("hello");
+    myList.add("hi");
+    myList.add("hey");
     // Print the element at index 1
-
+    System.out.println(myList.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)
-
+    myList.set(1, "bye");
     // Insert a new element at index 0 (the length of the list will change)
-
+    myList.add(0, "goodbye");
+    System.out.println(myList);
     // Check whether the list contains a certain string
-
+    System.out.println(myList.contains("hi"));
+    System.out.println(myList.contains("bye"));
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
-
+    for(int i = 0; i < myList.size(); i++){
+      System.out.println(i + ": " + myList.get(i));
+    }
     // Sort the list using the Collections library
-
+    myList.sort(null);
+    System.out.println(myList);
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+    for (String string : myList) {
+      System.out.println();
+      System.out.println(string);
+    }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,29 +1,38 @@
-
+import java.util.*;
+import java.util.Map.Entry;
 
 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<>();
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
-
+    myMap.put("penny", 1);
+    myMap.put("quarter", 25);
+    myMap.put("nickel", 0);
     // Get the value associated with a given key in the Map
-
+    System.out.println(myMap.get("quarter"));
     // 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.replace("nickel", 5);
     // Check whether the Map contains a given key
-
+    System.out.println(myMap.containsKey("penny"));
     // Check whether the Map contains a given value
-
+    System.out.println(myMap.containsValue(0));
     // Iterate over the keys of the Map, printing each key
-
+    for(String key : myMap.keySet()){
+      System.out.println(key);
+    }
     // Iterate over the values of the map, printing each value
-
+    for(Integer value : myMap.values()){
+      System.out.println(value);
+    }
     // Iterate over the entries in the map, printing each key and value
-
+    for(Entry<String, Integer> entry: myMap.entrySet()){
+      System.out.println(entry);
+    }
     /*
      * 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
-
+    Double negFloat =  -1.5;
+    System.out.println(negFloat);
     // Create an int with a positive value and assign it to a variable
-
+    int posInt = 6;
+    System.out.println(posInt);
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+    System.out.println(posInt % 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 ((posInt % 2)== 0){
+      System.out.println("Even");
+    } else {
+      System.out.println("Odd");
+    }
     // Divide the number by another number using integer division
-
+    System.out.println(posInt / 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
-
-
+  private int age;
+  String name;
   // Create a constructor that takes the name and age of the person
   // and assigns it to the instance variables
-
+  public Person(int age, String name){
+    this.age = age;
+    this.name = name;
+  }
 
   // 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 +34,31 @@ 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 firstPerson = new Person(10, "Joey");
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
 
+    Person anotherPerson = new Person(20, "Jane");
     // Print the first person
-
+    System.out.println(firstPerson);
     // Print the second person
-
+    System.out.println(anotherPerson);
     // Get the name of the first person and store it in a local variable
-
+    String firstName = firstPerson.name;
+    System.out.println(firstName);
     // 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 = firstPerson.birthYear(2025);
     // In a separate statement, print the local variable holding the birth year.
-
+    System.out.println(firstBirthYear);
     /**
      * Terminology!
      * 

src/SetPractice.java

@@ -1,18 +1,25 @@
+import java.util.*;
+
 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<>();
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
-
+    mySet.add("hi");
+    mySet.add("hello");
+    mySet.add("howdy");
     // Check whether the Set contains a given String
-
+    System.out.println(mySet.contains("howdy"));
     // Remove an element from the Set
-
+    mySet.remove("hi");
+    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
-
+    for(String string : mySet){
+      System.out.println(string);
+    }
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,26 +1,35 @@
+import java.util.*;
+
 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 = "At Least Five";
     // Find the length of the string
-
+    System.out.println(myString.length());
     // Concatenate (add) two strings together and reassign the result
-
+    String concatResult = myString + " Characters";
+    System.out.println(concatResult);
     // Find the value of the character at index 3
-
+    System.out.println(myString.charAt(3));
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
-
+    System.out.println(myString.contains("east"));
     // Iterate over the characters of the string, printing each one on a separate line
-
+    for(char c : myString.toCharArray()){
+      System.out.println(c);
+    }
     // Create an ArrayList of Strings and assign it to a variable
-
+    List<String> myArrayList = new ArrayList<>();
     // Add multiple strings to the List (OK to do one-by-one)
-
+    myArrayList.add("this ");
+    myArrayList.add("is ");
+    myArrayList.add("my ");
+    myArrayList.add("list.");
     // 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 = myArrayList.toString();
+    System.out.println(singleString);
     // Check whether two strings are equal
-
+    System.out.println(myString.equals(myArrayList.get(0)));
     /*
      * Reminder!
      * 

toRefresh.md

@@ -2,4 +2,6 @@
 
 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.
 
-- 
+- instantiating Lists and List methods
+- instantiating arrays
+- iterating through maps