Java Derusting Canvas

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[] list = 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
+      list[0] = "hola";
+      list[1] = "mi";
+      list[2] = "nombre";
+      list[3] = "Kevin";
 
     // Get the value of the array at index 2
-
+      System.out.println(list[2]);
     // Get the length of the array
-
+      System.out.println(list.length);
     // Iterate over the array using a traditional for loop and print out each item
-
+      for (int i = 0; i<list.length; i++){
+        System.out.println(list[i]);
+      }
+      System.out.println();
     // Iterate over the array using a for-each loop and print out each item
-
+      for (String str: list){
+        System.out.println(str);
+      }
+      System.out.println();
     /*
      * Reminder!
      * 

src/ListPractice.java

@@ -1,28 +1,41 @@
+import java.util.ArrayList;
+import java.util.List;
+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
-
-    // Add 3 elements to the list (OK to do one-by-one)
-
+      List<String> list = new ArrayList<>();
+    // Add 3 elements to the lisst (OK to do one-by-one)
+      list.add("hello");
+      list.add("I'm");
+      list.add("Kevin");
     // Print the element at index 1
-
+      System.out.println(list.get(1));
     // Replace the element at index 1 with a new value
+    list.set(1, "replaced");
+    System.out.println(list);
     // (Do not insert a new value. The length of the list should not change)
 
     // Insert a new element at index 0 (the length of the list will change)
-
+    list.add(0,"hi");
+    System.out.println(list);
     // Check whether the list contains a certain string
-
+    System.out.println(list.contains("hi"));
     // 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
-
+      System.out.println();
+      for (String str : list){
+        System.out.print(str + " ");
+      }
     /*
      * Usage tip!
      * 

src/MapPractice.java

@@ -1,29 +1,41 @@
-
+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> mapStr = new HashMap<>();
     // Put 3 different key/value pairs in the Map
     // (it's OK to do this one-by-one)
-
+    mapStr.put("one", 1);
+    mapStr.put("two", 2);
+    mapStr.put("three", 3);
+    System.out.println(mapStr);
     // Get the value associated with a given key in the Map
-
+    System.out.println(mapStr.get("one"));
     // Find the size (number of key/value pairs) of the Map
-
+    System.out.println(mapStr.size());
     // Replace the value associated with a given key (the size of the Map shoukld not change)
-
+    mapStr.replace("one", 5);
+    System.out.println(mapStr);
     // Check whether the Map contains a given key
-
+    System.out.println(mapStr.containsKey("one"));
     // Check whether the Map contains a given value
-
+    System.out.println(mapStr.containsValue(5));
     // Iterate over the keys of the Map, printing each key
-
+    System.out.println();
+    for (String key : mapStr.keySet()) {
+      System.out.println(key);
+    }
     // Iterate over the values of the map, printing each value
-
+    for (Integer value : mapStr.values()) {
+      System.out.println(value);
+    }
     // Iterate over the entries in the map, printing each key and value
-
+    for (Map.Entry<String, Integer> entry : mapStr.entrySet()){
+      System.out.println(entry.getKey() + " -> " + entry.getValue());
+    }
     /*
      * Usage tip!
      * 

src/NumberPractice.java

@@ -1,18 +1,26 @@
 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;
+      System.out.println(negativeFloat);
     // Create an int with a positive value and assign it to a variable
-
+      int positiveInt = 12;
+      System.out.println(positiveInt);
     // Use the modulo % operator to find the remainder when the int is divided by 3
-
+      positiveInt = positiveInt % 3;
+      System.out.println(positiveInt);
     // 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("true");
+      } else {
+        System.out.println("false");
+      }
     // Divide the number by another number using integer division
-
+      positiveInt = positiveInt / 3;
+      System.out.println(positiveInt);
     /*
      * Reminder!
      * 

src/Person.java

@@ -6,14 +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){
+    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: " + name +
+    " Age: " + age;
+  }
 
   // Implement the below public instance method "birthYear"
   // There should NOT be any print statement in this method.
@@ -28,26 +36,29 @@ 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 person1 = new Person("Gary", 2);
     // Create another instance of Person with a different name and age and
     // assign it to a different variable
+        Person person2 = new Person("Spongebob", 20);
 
     // Print the first person
-
+    System.out.println(person1);
     // Print the second person
-
+    System.out.println(person2);
     // Get the name of the first person and store it in a local variable
-
+    String name = person1.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 birthYear1 = person1.birthYear(2025);
     // In a separate statement, print the local variable holding the birth year.
-
+    System.out.println(birthYear1);
     /**
      * Terminology!
      * 

src/SetPractice.java

@@ -1,18 +1,25 @@
+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> setStr = new HashSet<>();
     // Add 3 elements to the set
     // (It's OK to do it one-by-one)
-
+    setStr.add("hi");
+    setStr.add("im");
+    setStr.add("Kevin");
+    System.out.println(setStr);
     // Check whether the Set contains a given String
-
+    System.out.println(setStr.contains("hi"));
     // Remove an element from the Set
-
+    setStr.remove("hi");
     // Get the size of the Set
-
+    System.out.println(setStr.size());
     // Iterate over the elements of the Set, printing each one on a separate line
-
+    for (String str : setStr) {
+      System.out.println(str);
+    }
     /*
      * Warning!
      * 

src/StringPractice.java

@@ -1,26 +1,37 @@
+import java.util.ArrayList;
+import java.util.List;
+
 public class StringPractice {
   public static void main(String[] args) {
     // Create a string with at least 5 characters and assign it to a variable
-
+    String str = "hello";
     // Find the length of the string
-
+    System.out.println(str.length());
     // Concatenate (add) two strings together and reassign the result
-
+    String newStr = str + "Kevin";
+    System.out.println(newStr);
     // Find the value of the character at index 3
-
+    System.out.println(str.charAt(3));
     // Check whether the string contains a given substring (i.e. does the string have "abc" in it?)
-
+    System.out.println(str.contains("abc"));
     // Iterate over the characters of the string, printing each one on a separate line
-
+    for (int i = 0; i<str.length(); i++){
+      System.out.println(str.charAt(i));
+    }
     // Create an ArrayList of Strings and assign it to a variable
-
+    List<String> list = new ArrayList<>();
     // Add multiple strings to the List (OK to do one-by-one)
-
+    list.add("my");
+    list.add("name");
+    list.add("is");
+    list.add("Kevin");
+    System.out.println(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 combinedList = String.join(", ", list);
+      System.out.println(combinedList);
     // Check whether two strings are equal
-
+      System.out.println(str.equals(combinedList));
     /*
      * 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.
 
-- 
+- how to insert at certain points in ArrayList
+- .join() for string
+- how to interate over maps and entries