Derusting assignment

README.md

@@ -20,6 +20,7 @@ Most of these taks should be easy, but there will likely be some that ask you to
 - SetPractice
 - MapPractice
 - Person.java
+- Making classes
 
 ## Submitting
 Make a Pull Request (PR) against the original repository. Copy the link into Canvas to submit.

src/ArrayPractice.java

@@ -1,18 +1,31 @@
 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] = "aardvark";
+    strings[1] = "bison";
+    strings[2] = "donkey";
+    strings[3] = "cheetah";
 
     // Get the value of the array at index 2
-
+    String indexTwo = strings[2];
+    System.out.println(indexTwo);
+
     // Get the length of the array
+    int length = strings.length;
+    System.out.println(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 string : strings) {
+      System.out.println(string);
+    }
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,45 @@
+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("homework");
+    list.add("pencils");
+    list.add("erasers");
 
     // 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, "pencil case");
 
     // Insert a new element at index 0 (the length of the list will change)
+    list.add(0, "notebook");
 
     // Check whether the list contains a certain string
+    System.out.println("Does the list contain a notebook?: " + list.contains("notebook"));
 
     // 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(i + "=" + list.get(i));
+    }
 
     // Sort the list using the Collections library
+    Collections.sort(list);
 
     // Iterate over the list using a for-each loop
     // Print each value on a second line
-
+    for (String item : list) {
+      System.out.println(item);
+    }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,29 +1,55 @@
-
+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> map = new HashMap<>();
+
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
+    map.put("Cheese", 2);
+    map.put("Onions",1);
+    map.put("Bread",5);
 
-    // Get the value associated with a given key in the Map
 
+    // Get the value associated with a given key in the Map
+    System.out.println("Cheese costs " + map.get("Cheese") + " dollars.");
+
     // Find the size (number of key/value pairs) of the Map
+    System.out.println("There are " + map.size() + " pairs in the Map.");
 
     // Replace the value associated with a given key (the size of the Map shoukld not change)
+    map.put("Cheese", 3);
+    System.out.println("Cheese now costs " + map.get("Cheese") + " dollars.");
 
     // Check whether the Map contains a given key
-
+    if (map.containsKey("Onions")) {
+      System.out.println("Map contains onions.");
+    } else {
+      System.out.println("Map does not contain onions.");
+    }
+
     // Check whether the Map contains a given value
-
+    if (map.containsValue(2)) {
+      System.out.println("One of the items has a value of 2.");
+    } else {
+      System.out.println("None of the items has a value of 2.");
+    }
     // Iterate over the keys of the Map, printing each key
+    for (String string : map.keySet()) {
+      System.out.println(string);
+    }
 
     // Iterate over the values of the map, printing each value
+    for (int value : map.values()) {
+      System.out.println(value);
+    }
 
     // Iterate over the entries in the map, printing each key and value
-
+    for (String string : map.keySet()) {
+      System.out.println(string + "=" + map.get(string));
+    }
     /*
      * Usage tip!
      * 

src/NumberPractice.java

@@ -1,18 +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 = -3.14f;
+    System.out.println("A negative float is: " + negativeFloat);
+
     // Create an int with a positive value and assign it to a variable
-
+    int positiveInt = 3;
+    System.out.println("A positive int is: " + positiveInt);
+
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+    int remainder = positiveInt % 3;
+    System.out.println("When you divide " + positiveInt + " by 3, the remainder is: " + 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 (positiveInt % 2 == 0) {
+      System.out.println("Even");
+    } else {
+      System.out.println("Odd");
+    }
+
     // Divide the number by another number using integer division
+    int anotherInt = 2;
 
+    int result = positiveInt / anotherInt;
+    System.out.println("When you divide " + positiveInt + " by " + anotherInt + " the answer is rounded down to: " + result);
     /*
      * Reminder!
      * 

src/Person.java

@@ -6,14 +6,26 @@
 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) {
+    this.name = name;
+    this.age = age;
+  }
 
+  // added getters
+  public String getName() { return name; }
 
-  // Create a toString method that gives the name and age of the person
+  public int getAge() { return age; }
 
+  // Create a toString method that gives the name and age of the person
+  @Override
+  public String toString() {
+    return "Name:" + name + " Age:" + age;
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -28,25 +40,36 @@ 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 steve = new Person("Steve",27);
 
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+    Person jackie = new Person("Jackie", 28);
 
     // Print the first person
+    System.out.println(steve);
 
     // Print the second person
+    System.out.println(jackie);
 
     // Get the name of the first person and store it in a local variable
-
+    String steveName = steve.getName();
+    System.out.println(steveName);
+
     // 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 birthYear = steve.birthYear(2025);
+
 
     // In a separate statement, print the local variable holding the birth year.
+    System.out.println(birthYear);
 
     /**
      * Terminology!

src/SetPractice.java

@@ -1,18 +1,33 @@
+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> set = new HashSet<String>();
 
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
+    set.add("coffee");
+    set.add("tea");
+    set.add("juice");
 
     // Check whether the Set contains a given String
-
+    if (set.contains("juice")) {
+      System.out.println("Set contains 'juice'.");
+    } else {
+      System.out.println("Set does not contain 'juice'");
+    }
     // Remove an element from the Set
+    set.remove("juice");
 
     // Get the size of the Set
+    System.out.println("The set contains " + set.size() + " items.");
 
     // Iterate over the elements of the Set, printing each one on a separate line
-
+    for (String string : set) {
+      System.out.println(string);
+    }
+
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,27 +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 string = "example";
 
     // Find the length of the string
+    int stringLength = string.length();
+    System.out.println(stringLength);
 
     // Concatenate (add) two strings together and reassign the result
+    string = string + " 1; " + string + " 2";
+    System.out.println(string);
 
     // Find the value of the character at index 3
+    System.out.println(string.charAt(3));
 
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
+    Boolean containsSubstring = string.contains("example");
+    System.out.println("The sentence contains example?: " + containsSubstring);
 
     // Iterate over the characters of the string, printing each one on a separate line
-
+    for (int i = 0; i < string.length(); i++) {
+      System.out.println(string.charAt(i));
+    }
     // Create an ArrayList of Strings and assign it to a variable
+    ArrayList<String> stringArray = new ArrayList<>();
 
     // Add multiple strings to the List (OK to do one-by-one)
+    stringArray.add("example 1");
+    stringArray.add("example 2");
+    stringArray.add("example 3");
 
     // 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 joinedString = String.join(", ", stringArray);
+    System.out.println(joinedString);
 
     // Check whether two strings are equal
+    String first = "test";
+    String second = "text";
 
-    /*
+    System.out.println("String 'test' equals 'text'?: " + first.equals(second));
+    /*java
      * Reminder!
      * 
      * When comparing objects in Java we typically want to use .equals, NOT ==.

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.
 
-- 
+- how to make a float (used to using double)
+- difference between list and arraylist syntax
+- array syntax
+- string utilities
+- set syntax
+- forEach for maps