diff --git a/src/ArrayPractice.java b/src/ArrayPractice.java index bc58c83..380ae7b 100644 --- a/src/ArrayPractice.java +++ b/src/ArrayPractice.java @@ -1,18 +1,25 @@ -public class ArrayPractice { +public class ArrayPractice { public static void main(String[] args) { // Create an array of Strings of size 4 - + String [] wordStrings = 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 - + wordStrings[0] = "10"; + wordStrings[1] = "20"; + wordStrings[2] = "30"; + wordStrings[3] = "40"; // Get the value of the array at index 2 - + System.out.println("The value at index 2 is " + wordStrings[2]); // Get the length of the array - + System.out.println("The length of the array is " + wordStrings.length); // Iterate over the array using a traditional for loop and print out each item - + for (int i = 0; i < wordStrings.length; i++) { + System.out.println("The value at index " + i + " is " + wordStrings[i]); + } // Iterate over the array using a for-each loop and print out each item - + for (String word : wordStrings) { + System.out.println("The value is " + word); + } /* * Reminder! * diff --git a/src/ListPractice.java b/src/ListPractice.java index f4de8e7..f5a1498 100644 --- a/src/ListPractice.java +++ b/src/ListPractice.java @@ -1,28 +1,40 @@ +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 list = new ArrayList(); // Add 3 elements to the list (OK to do one-by-one) - +list.add("Apple"); +list.add("Banana"); +list.add("Cherry"); // Print the element at index 1 - - // Replace the element at index 1 with a new value +System.out.println(list.get(1)); + // Replace he 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, "Grapes"); // Insert a new element at index 0 (the length of the list will change) - +list.add(0, "Mango"); // Check whether the list contains a certain string - +list.contains("Pineapple"); // 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("index" + 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 (int i = 0; i < list.size(); i++) { + System.out.println(list.get(i)); + } + } /* * Usage tip! * @@ -33,4 +45,3 @@ public static void main(String[] args) { * index values a for-each loop is cleaner. */ } -} \ No newline at end of file diff --git a/src/MapPractice.java b/src/MapPractice.java index 7ebfeac..c34d902 100644 --- a/src/MapPractice.java +++ b/src/MapPractice.java @@ -1,29 +1,46 @@ - +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 map = new HashMap<>(); // Put 3 different key/value pairs in the Map // (it's OK to do this one-by-one) - + map.put("Apple", 1); + map.put("Pineapple", 2); + map.put("Pear", 3); + // Get the value associated with a given key in the Map - + System.out.println("The value associated with Apple is " + map.get("Apple")); // 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) - + System.out.println("The size of the map is " + map.size()); + // Replace the value associated with a given key (the size of the Map should not change) + map.put("Apple", 5); // Check whether the Map contains a given key - + if (map.containsKey("Apple")) { + System.out.println("The map contains Apple"); + }else{ + System.out.println("The map does not contain Apple"); + } // Check whether the Map contains a given value - + if (map.containsValue(5)) { + System.out.println("The map contains the value of 5") + }else{ + System.out.println("The map does not contain the value of 5"); + } // 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 value : map.values()) { + System.out.println(value); + } // Iterate over the entries in the map, printing each key and value - + for (HashMap.Entry entry : map.entrySet()) { + System.out.println("Key: " + entry.getKey() + ", Value: " + entry.getValue()); + } /* * Usage tip! * diff --git a/src/NumberPractice.java b/src/NumberPractice.java index bbec2fe..c46a5f1 100644 --- a/src/NumberPractice.java +++ b/src/NumberPractice.java @@ -1,18 +1,25 @@ -public class NumberPractice { - public static void main(String args[]) { +public class NumberPractice { +public static void main(String args[]) { // Create a float with a negative value and assign it to a variable - +float negative_Float = -20; // Create an int with a positive value and assign it to a variable - +int positive_Int = 200; // Use the modulo % operator to find the remainder when the int is divided by 3 +int remainder = positive_Int % 3; // 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 evenCheck = positive_Int % 2; +if (evenCheck == 0) { + System.out.println("Even"); +}else { + System.out.println("Odd"); +} // Divide the number by another number using integer division - +int num_Division = positive_Int / 7; +System.out.println(num_Division); /* * Reminder! * diff --git a/src/Person.java b/src/Person.java index 8ab3f95..992f809 100644 --- a/src/Person.java +++ b/src/Person.java @@ -6,16 +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; +} // 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" + public int birthYear(int currentYear) { + return currentYear - age; + } // There should NOT be any print statement in this method. /** * birthYear returns the year the person was born. @@ -28,26 +38,29 @@ 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("Alice", 30); // 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 firstPersonName = 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("Birth year of " + firstPersonName + " is " + birthYear); /** * Terminology! * diff --git a/src/SetPractice.java b/src/SetPractice.java index d2fc1c9..67c3bb2 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 set = new HashSet(); // Add 3 elements to the set // (It's OK to do it one-by-one) + set.add("Apple"); + set.add("Banana"); + set.add("Cherry"); + // Check whether the Set contains a given String + if (set.contains("Banana")) { + System.out.println("The set contains Banana"); + } else { + System.out.println("The set does not contain Banana"); + } // Remove an element from the Set - + set.remove("Apple"); + // Get the size of the Set - + System.out.println("The size of the set is " + set.size()); // Iterate over the elements of the Set, printing each one on a separate line - + for (String item : set) { + System.out.println(item); + } /* * Warning! * diff --git a/src/StringPractice.java b/src/StringPractice.java index 8d87617..7808da6 100644 --- a/src/StringPractice.java +++ b/src/StringPractice.java @@ -1,26 +1,52 @@ +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[] fruits = {"Apple", "Mango", "Pineapple", "Kiwi", "Watermelon"}; // Find the length of the string - + for ( String fruit : fruits) { + System.out.println("The length of " + fruit + " is " + fruit.length()); + } // Concatenate (add) two strings together and reassign the result - + String joinString = String.join(", ", fruits); + System.out.println(joinString); // Find the value of the character at index 3 - + String fruit = fruits[0]; + System.out.println("The character at index 3 of " + fruit + " is " + fruit.charAt(3)); // Check whether the string contains a given substring (i.e. does the string have "abc" in it?) - + for (String fruit : fruits) { + if (fruit.contains("abc")) { + System.out.println("The string contains abc"); + } else { + System.out.println("The string does not contain abc"); + } + } + // Iterate over the characters of the string, printing each one on a separate line - + for (String fruit : fruits) { + for (int i = 0; i < fruit.length(); i++) { + System.out.println(fruit.charAt(i)); + } +} // Create an ArrayList of Strings and assign it to a variable - + ArrayList List = new ArrayList(); // Add multiple strings to the List (OK to do one-by-one) - + List.add("Apple"); + List.add("Mango"); + List.add("Banana"); // 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(", ", List); + System.out.println(joinedString); // Check whether two strings are equal - + if (List.get(0).equals("Apple")) { + System.out.println("The first string is Apple"); + } else { + System.out.println("The first string is not Apple"); + } + /* * Reminder! *