diff --git a/src/ArrayPractice.java b/src/ArrayPractice.java index bc58c83..281b284 100644 --- a/src/ArrayPractice.java +++ b/src/ArrayPractice.java @@ -1,18 +1,30 @@ public class ArrayPractice { public static void main(String[] args) { // Create an array of Strings of size 4 + String[] stringArray = new String[4]; // Set the value of the array at each index to be a different String + stringArray[0]= "one"; + stringArray[1]="Two"; + stringArray[2]="Three"; + stringArray[3]="Four"; // It's OK to do this one-by-one // Get the value of the array at index 2 + System.out.println("Value at index 2: " + stringArray[2]); // Get the length of the array + System.out.println("Length of the array: " + stringArray.length); // Iterate over the array using a traditional for loop and print out each item - + for(int i=0; i stringList = new ArrayList<>(); // Add 3 elements to the list (OK to do one-by-one) + stringList.add("Apple"); + stringList.add("Banana"); + stringList.add("Cherry"); // Print the element at index 1 + System.out.println("Element at index 1: " + stringList.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) - + stringList.set(1, "Blueberry"); // Insert a new element at index 0 (the length of the list will change) - + stringList.add(0, "Avocado"); // Check whether the list contains a certain string - + boolean containsCherry = stringList.contains("Cherry"); + System.out.println("Does the list contain 'Cherry'? " + containsCherry); // Iterate over the list using a traditional for-loop. // Print each index and value on a separate line - + System.out.println("\nTraditional for-loop:"); + for (int i = 0; i < stringList.size(); i++) { + System.out.println("Index " + i + ": " + stringList.get(i)); + } // Sort the list using the Collections library - + Collections.sort(stringList); + System.out.println("\nSorted list: " + stringList); // Iterate over the list using a for-each loop // Print each value on a second line - + System.out.println("\nFor-each loop:"); + for (String fruit : stringList) { + System.out.println(fruit); + } /* * Usage tip! * diff --git a/src/MapPractice.java b/src/MapPractice.java index 7ebfeac..45592a1 100644 --- a/src/MapPractice.java +++ b/src/MapPractice.java @@ -1,29 +1,49 @@ - +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 - - // Put 3 different key/value pairs in the Map - // (it's OK to do this one-by-one) - - // Get the value associated with a given key in the Map - - // Find the size (number of key/value pairs) of the Map - - // Replace the value associated with a given key (the size of the Map shoukld not change) - - // Check whether the Map contains a given key - - // Check whether the Map contains a given value - - // Iterate over the keys of the Map, printing each key - - // Iterate over the values of the map, printing each value - - // Iterate over the entries in the map, printing each key and value - + // 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("Apple", 5); + map.put("Banana", 3); + map.put("Cherry", 8); + + // Get the value associated with a given key in the Map + System.out.println("Value associated with 'Banana': " + map.get("Banana")); + + // Find the size (number of key/value pairs) of the Map + System.out.println("Size of the map: " + map.size()); + + // Replace the value associated with a given key (the size of the Map should not change) + map.put("Banana", 6); + System.out.println("Updated value for 'Banana': " + map.get("Banana")); + + // Check whether the Map contains a given key + System.out.println("Does the map contain key 'Apple'? " + map.containsKey("Apple")); + + // Check whether the Map contains a given value + System.out.println("Does the map contain value 8? " + map.containsValue(8)); + + // Iterate over the keys of the Map, printing each key + System.out.println("\nKeys in the map:"); + for (String key : map.keySet()) { + System.out.println(key); + } + + // Iterate over the values of the map, printing each value + System.out.println("\nValues in the map:"); + for (Integer value : map.values()) { + System.out.println(value); + } + + // Iterate over the entries in the map, printing each key and value + System.out.println("\nEntries in the map:"); + 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..fc98c6b 100644 --- a/src/NumberPractice.java +++ b/src/NumberPractice.java @@ -1,18 +1,27 @@ public class NumberPractice { public static void main(String args[]) { // Create a float with a negative value and assign it to a variable + float negativeFloat = -7.5f; // Create an int with a positive value and assign it to a variable + int positiveInt = 10; // Use the modulo % operator to find the remainder when the int is divided by 3 + int remainder = positiveInt % 3; + System.out.println("Remainder when " + positiveInt + " is divided by 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. + // 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(positiveInt + " is Even"); + } else { + System.out.println(positiveInt + " is Odd"); + } // Divide the number by another number using integer division - + int divisionResult = positiveInt / 3; + System.out.println(positiveInt + " divided by 3 (integer division): " + divisionResult); /* * Reminder! * diff --git a/src/Person.java b/src/Person.java index 8ab3f95..cfa2489 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 + public String name; // Declare a private int instance variable for the age of the person - + public 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 +35,31 @@ 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 person1 = new Person("Alice", 23); // Create another instance of Person with a different name and age and // assign it to a different variable - + Person person2 = new Person("Bob", 25); // 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 personName = 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 birthYear = person1.birthYear(2025); // In a separate statement, print the local variable holding the birth year. - + System.out.println(personName + " was born in: " + birthYear); /** * Terminology! * diff --git a/src/SetPractice.java b/src/SetPractice.java index d2fc1c9..d631678 100644 --- a/src/SetPractice.java +++ b/src/SetPractice.java @@ -1,18 +1,33 @@ +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 mySet =new HashSet<>(); // Add 3 elements to the set + mySet.add("Apple"); + mySet.add("Banana"); + mySet.add("Cherry"); + // (It's OK to do it one-by-one) // Check whether the Set contains a given String - + boolean containsApple = mySet.contains("Apple"); + System.out.println("Set contains 'Apple': " + containsApple); // Remove an element from the Set - + mySet.remove("Banana"); + System.out.println("After removing 'Banana': " + mySet); // Get the size of the Set + int size = mySet.size(); + System.out.println("The size of the Set is: " + size); - // Iterate over the elements of the Set, printing each one on a separate line + // Iterate over the elements of the Set, printing each one on a separate line + System.out.println("Set elements:"); + for (String item : mySet) { + System.out.println(item); + } /* * Warning! * diff --git a/src/StringPractice.java b/src/StringPractice.java index 8d87617..816bb7a 100644 --- a/src/StringPractice.java +++ b/src/StringPractice.java @@ -1,26 +1,45 @@ +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 myString = "Hello"; // Find the length of the string + int length = myString.length(); + System.out.println("Length of the string: " + length); // Concatenate (add) two strings together and reassign the result + myString = myString + " World"; + System.out.println("After concatenation: " + myString); // Find the value of the character at index 3 - + char charAtIndex3 = myString.charAt(3); + System.out.println("Character at index 3: " + charAtIndex3); // Check whether the string contains a given substring (i.e. does the string have "abc" in it?) - + boolean containsSubstring = myString.contains("abc"); + System.out.println("Contains 'abc': " + containsSubstring); // Iterate over the characters of the string, printing each one on a separate line - + System.out.println("Characters in the string:"); + for (int i = 0; i < myString.length(); i++) { + System.out.println(myString.charAt(i)); + } // Create an ArrayList of Strings and assign it to a variable - + ArrayList stringList = new ArrayList<>(); // Add multiple strings to the List (OK to do one-by-one) - + stringList.add("Apple"); + stringList.add("Banana"); + stringList.add("Cherry"); // 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(", ", stringList); + System.out.println("Joined string: " + joinedString); // Check whether two strings are equal - + String string1 = "hello"; + String string2 = "hello"; + boolean areEqual = string1.equals(string2); + System.out.println("Are the strings equal? " + areEqual); + /* * Reminder! *