derusting completion

src/ArrayPractice.java

@@ -1,17 +1,30 @@
 public class ArrayPractice {
   public static void main(String[] args) {
     // Create an array of Strings of size 4
+    String[] strings = 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
+    strings[0] = "Hey";
+    strings[1] = "Test";
+    strings[2] = "Third";
+    strings[3] = "Fourth";
 
     // Get the value of the array at index 2
+    System.out.println(strings[2]);
 
     // Get the length of the array
+    System.out.println(strings.length);
 
     // Iterate over the array using a traditional for loop and print out each item
+    for(int i = 0; i < strings.length; i++) {
+      System.out.println(strings[i]);
+    }
 
     // Iterate over the array using a for-each loop and print out each item
+    for(String str : strings) {
+      System.out.println(str);
+    }
 
     /*
      * Reminder!

src/ListPractice.java

@@ -1,27 +1,50 @@
+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> strings = new ArrayList<String>();
 
     // Add 3 elements to the list (OK to do one-by-one)
+    strings.add("Hey");
+    strings.add("hey2");
+    strings.add("whats up");
 
     // Print the element at index 1
+    System.out.println(strings.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)
+    strings.set(1, "new value");
+    System.out.println(strings.get(1));
 
     // Insert a new element at index 0 (the length of the list will change)
+    strings.add(0, "even newer value");
+    System.out.println(strings.get(0));
+
 
     // Check whether the list contains a certain string
+    if(strings.indexOf("new value") >= 0) {
+      System.out.println("Found.");
+    } else {
+      System.out.println("Not found.");
+    }
 
     // Iterate over the list using a traditional for-loop.
     // Print each index and value on a separate line
+    for(int i = 0; i < strings.size(); i++) {
+      System.out.println(i + strings.get(i));
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(strings);
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
+    for(String str : strings) {
+      System.out.println(str);
+    }
 
     /*
      * Usage tip!

src/MapPractice.java

@@ -1,28 +1,47 @@
-
+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
+    HashMap<String, Integer> strIntHashMap = new HashMap<>();
 
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    strIntHashMap.put("test1", 1);
+    strIntHashMap.put("test2", 2);
+    strIntHashMap.put("test3", 3);
 
     // Get the value associated with a given key in the Map
+    System.out.println(strIntHashMap.get("test2"));
 
     // Find the size (number of key/value pairs) of the Map
+    System.out.println(strIntHashMap.size());
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+    strIntHashMap.replace("test2", 4);
+    System.out.println(strIntHashMap.size());
 
     // Check whether the Map contains a given key
+    System.out.println(strIntHashMap.containsKey("test1"));
 
     // Check whether the Map contains a given value
+    System.out.println(strIntHashMap.containsValue(2));
 
     // Iterate over the keys of the Map, printing each key
+    for(String key : strIntHashMap.keySet()) {
+      System.out.println(key);
+    }
 
     // Iterate over the values of the map, printing each value
+    for(Integer value : strIntHashMap.values()) {
+      System.out.println(value);
+    }
 
     // Iterate over the entries in the map, printing each key and value
+    for(HashMap.Entry<String, Integer> entry : strIntHashMap.entrySet()) {
+      System.out.println(entry.getKey() + " - " + entry.getValue());
+    }
 
     /*
      * Usage tip!

src/NumberPractice.java

@@ -1,17 +1,33 @@
 public class NumberPractice {
   public static void main(String args[]) {
     // Create a float with a negative value and assign it to a variable
+    float negativeFloat = -1.5f;
+    //System.out.println(negativeFloat);
 
     // Create an int with a positive value and assign it to a variable
+    int positiveInt = 5;
+    //System.out.println(positiveInt);
 
     // Use the modulo % operator to find the remainder when the int is divided by 3
+    int remainder = positiveInt % 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 isEvenNumber = 1;
+    if(isEvenNumber % 2 == 0) {
+      System.out.println("Even");
+    } else {
+      System.out.println("Odd");
+    }
 
     // Divide the number by another number using integer division
+    int number1 = 20;
+    int number2 = 10;
+    int result = number1 / number2;
+    System.out.println(result);
 
     /*
      * Reminder!

src/Person.java

@@ -6,13 +6,22 @@
 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) {
+      age = _age;
+      name = _name;
+  }
 
 
   // 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"
@@ -28,25 +37,36 @@ public class Person {
    * @return The year the person was born
    */
   // (create the instance method here)
+  public int birthYear(int currentYear) {
+    int bornOn = currentYear - age;
+    return bornOn;
+  }
 
 
   public static void main(String[] args) {
     // Create an instance of Person
+    Person person = new Person("Person1", 20);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person person2 = new Person("Person2", 25);
 
     // Print the first person
+    System.out.println(person);
 
     // Print the second person
+    System.out.println(person2);
 
     // Get the name of the first person and store it in a local variable
+    String firstPersonName = person.name;
 
     // 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 bornOn = person.birthYear(2025);
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(bornOn);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,17 +1,29 @@
+import java.util.HashSet;
+
 public class SetPractice {
   public static void main(String[] args) {
     // Create a HashSet of Strings and assign it to a variable of type Set
+    HashSet<String> hashStrings = new HashSet<>();
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    hashStrings.add("test1");
+    hashStrings.add("test2");
+    hashStrings.add("test3");
 
     // Check whether the Set contains a given String
+    System.out.println(hashStrings.contains("test1"));
 
     // Remove an element from the Set
+    hashStrings.remove("test3");
 
     // Get the size of the Set
+    System.out.println(hashStrings.size());
 
     // Iterate over the elements of the Set, printing each one on a separate line
+    for(String str : hashStrings) {
+      System.out.println(str);
+    }
 
     /*
      * Warning!

src/StringPractice.java

@@ -1,25 +1,48 @@
+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 fiveCharacterString = "Tests";
 
     // Find the length of the string
+    System.out.println(fiveCharacterString.length());
 
     // Concatenate (add) two strings together and reassign the result
+    String stringOne = "String1";
+    String stringTwo = "String2";
+    stringOne = stringOne.concat(stringTwo);
+    System.out.println(stringOne);
 
     // Find the value of the character at index 3
+    System.out.println(fiveCharacterString.charAt(3));
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    System.out.println(fiveCharacterString.contains("abc"));
 
     // Iterate over the characters of the string, printing each one on a separate line
+    for (int i = 0; i < fiveCharacterString.length(); i++) {
+      System.out.println(fiveCharacterString.charAt(i) + " ");
+    }
 
     // Create an ArrayList of Strings and assign it to a variable
+    ArrayList<String> arrayOfStrings = new ArrayList<String>();
 
     // Add multiple strings to the List (OK to do one-by-one)
+    arrayOfStrings.add("string1");
+    arrayOfStrings.add("string2");
+    arrayOfStrings.add("String3");
 
     // 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
+    System.out.println(arrayOfStrings.toString());
 
     // Check whether two strings are equal
+    if(stringOne.equals(stringTwo)) {
+      System.out.println("equal");
+    } else {
+      System.out.println("Not equal.");
+    }
 
     /*
      * Reminder!