diff --git a/src/ArrayPractice.java b/src/ArrayPractice.java index bc58c83..f549c8f 100644 --- a/src/ArrayPractice.java +++ b/src/ArrayPractice.java @@ -1,17 +1,29 @@ public class ArrayPractice { public static void main(String[] args) { // Create an array of Strings of size 4 + String words[] = 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 + words[0] = "Bike"; + words[1] = "Car"; + words[2] = "Boat"; + words[3] = "Motorcycle"; // Get the value of the array at index 2 + System.out.println(words[1]); // Get the length of the array + System.out.println(words.length); // Iterate over the array using a traditional for loop and print out each item - + for (int i = 0; i < words.length; i++) { + System.out.println(words[i]); + } // Iterate over the array using a for-each loop and print out each item + for (String word : words) { + System.out.println(word); + } /* * Reminder! diff --git a/src/ListPractice.java b/src/ListPractice.java index f4de8e7..4155c8e 100644 --- a/src/ListPractice.java +++ b/src/ListPractice.java @@ -1,28 +1,50 @@ +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; + 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 words = new ArrayList<>(); + // Add 3 elements to the list (OK to do one-by-one) - + words.add("Marvel Comics"); + words.add("Detective Comics"); + words.add("Image Comics"); // Print the element at index 1 + System.out.println(words.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) + words.set(1, "Dark Horse Comics"); + System.out.println(words.get(1)); // Insert a new element at index 0 (the length of the list will change) + words.add(0, "IDW Publishing"); // Check whether the list contains a certain string + System.out.println(words.contains("Dark Horse Comics")); // Iterate over the list using a traditional for-loop. - // Print each index and value on a separate line + for (int i = 0; i < words.size(); i++) { + // Print each index and value on a separate line + System.out.println(words.get(i)); + } // Sort the list using the Collections library + System.out.println("before sort: " + words); + Collections.sort(words); + System.out.println("after sort: " + words); // Iterate over the list using a for-each loop - // Print each value on a second line + for (String word : words) { + // Print each value on a second line + System.out.println(word); + } /* * Usage tip! * diff --git a/src/MapPractice.java b/src/MapPractice.java index 7ebfeac..bf1e089 100644 --- a/src/MapPractice.java +++ b/src/MapPractice.java @@ -1,28 +1,51 @@ - +import java.util.HashMap; +import java.util.Map; +import java.util.Set; 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 map = new HashMap<>(); // Put 3 different key/value pairs in the Map // (it's OK to do this one-by-one) + map.put("Xavier", 1); + map.put("Jhoanna", 2); + map.put("Thor", 3); // Get the value associated with a given key in the Map + int value = map.get("Xavier"); + System.out.println("The value associated with key: 'Xavier' is " + value); // Find the size (number of key/value pairs) of the Map + System.out.println("The size of the map is: " + map.size()); // Replace the value associated with a given key (the size of the Map shoukld not change) + map.replace("Thor", 23); + System.out.println(map.get("Thor")); + System.out.println(map.size()); // Check whether the Map contains a given key + System.out.println(map.containsKey("Xavier")); // Check whether the Map contains a given value + System.out.println(map.containsValue(23)); // Iterate over the keys of the Map, printing each key + for (String key : map.keySet()) { + System.out.println(key); + } // Iterate over the values of the map, printing each value + for (Integer val : map.values()) { + System.out.println(val); + } // Iterate over the entries in the map, printing each key and value + for (Map.Entry entry : map.entrySet()) { + System.out.println(entry.getKey() + " --> " + entry.getValue()); + } /* * Usage tip! diff --git a/src/NumberPractice.java b/src/NumberPractice.java index bbec2fe..16bf0c6 100644 --- a/src/NumberPractice.java +++ b/src/NumberPractice.java @@ -1,17 +1,29 @@ public class NumberPractice { public static void main(String args[]) { // Create a float with a negative value and assign it to a variable + float negativeNum = -10.0f; // Create an int with a positive value and assign it to a variable + int positiveNum = 10; // Use the modulo % operator to find the remainder when the int is divided by 3 + int remainder = positiveNum % 3; + System.out.println(positiveNum + " % 3 = " + 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 (negativeNum % 2 == 0) { + System.out.println("Even"); + } + else { + System.out.println("Odd"); + } // Divide the number by another number using integer division + int quotient = positiveNum / 5; + System.out.println("Answer: " + quotient); /* * Reminder! diff --git a/src/Person.java b/src/Person.java index 8ab3f95..3cde769 100644 --- a/src/Person.java +++ b/src/Person.java @@ -5,15 +5,22 @@ 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; // instance variable (can be accessed outside class ) + // Declare a private int instance variable for the age of the person + private int age;// can only be accessed within the class (private) // Create a constructor that takes the name and age of the person + public Person(String name, int age) { // and assigns it to the instance variables - - + this.name = name; + this.age = age; + } + // Create a toString method that gives the name and age of the person - + 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 +35,41 @@ public class Person { * @return The year the person was born */ // (create the instance method here) + public int birthYear(int currentYear) { + int yearOfBirth = currentYear - age; + return yearOfBirth; + } + + // Getter Method + public String getName() { + return this.name; + } public static void main(String[] args) { // Create an instance of Person + Person p = new Person("Xavier", 35); // Create another instance of Person with a different name and age and // assign it to a different variable + Person pTwo = new Person("Jhoanna", 36); // Print the first person + System.out.println(p); // Print the second person + System.out.println(pTwo); // Get the name of the first person and store it in a local variable - + System.out.println(p.getName()); + // 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 bornYear = p.birthYear(2025); // In a separate statement, print the local variable holding the birth year. + System.out.println("The year of birth for " + p.getName() + " is: " + bornYear); /** * Terminology! diff --git a/src/SetPractice.java b/src/SetPractice.java index d2fc1c9..bc534b6 100644 --- a/src/SetPractice.java +++ b/src/SetPractice.java @@ -1,17 +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 words = new HashSet<>(); // Add 3 elements to the set // (It's OK to do it one-by-one) - + words.add("The"); + words.add("Fantastic"); + words.add("Four"); + // Check whether the Set contains a given String + System.out.println(words.contains("Fantastic")); // Remove an element from the Set + words.remove("Four"); // Get the size of the Set + System.out.println(words.size()); // Iterate over the elements of the Set, printing each one on a separate line + for (String word : words) { + System.out.println(word); + } /* * Warning! diff --git a/src/StringPractice.java b/src/StringPractice.java index 8d87617..1dc7cea 100644 --- a/src/StringPractice.java +++ b/src/StringPractice.java @@ -1,26 +1,53 @@ +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 firstName = "Xavier"; // Find the length of the string + int nameLength = firstName.length(); + System.out.println("Length of name: " + nameLength); // Concatenate (add) two strings together and reassign the result + String lastName = "Lewis"; + + String fullName = firstName + " " + lastName; + + System.out.println(fullName); // Find the value of the character at index 3 + char c = fullName.charAt(3); + System.out.println("The value of the character at index 3 is: " + c); // Check whether the string contains a given substring (i.e. does the string have "abc" in it?) + System.out.println(fullName.contains("abc")); // Iterate over the characters of the string, printing each one on a separate line + for (int i = 0; i < lastName.length(); i++) { + char w = lastName.charAt(i); + System.out.println("Character at index " + i + " is " + w); + } // Create an ArrayList of Strings and assign it to a variable + ArrayList words = new ArrayList<>(); // Add multiple strings to the List (OK to do one-by-one) + words.add("Apple"); + words.add("Banana"); + words.add("Orange"); // 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 joinedStrings = String.join("," , words); + System.out.println(joinedStrings); // Check whether two strings are equal - + if (firstName.equals(lastName)) { + System.out.println("equal"); + } else { + System.out.println("not equal"); + } + /* * Reminder! *