diff --git a/src/ArrayPractice.java b/src/ArrayPractice.java index bc58c83..b3c9002 100644 --- a/src/ArrayPractice.java +++ b/src/ArrayPractice.java @@ -1,18 +1,25 @@ public class ArrayPractice { public static void main(String[] args) { // Create an array of Strings of size 4 - + String[] array = 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 - + array[0] = "Jameson"; + array[1] = "Auberon"; + array[2] = "Tina"; + array[3] = "Josh"; // Get the value of the array at index 2 - + String index2 = array[2]; // Get the length of the array - + int arrayLength = array.length; // Iterate over the array using a traditional for loop and print out each item - + for (int i = 0; i < array.length; i++) { + System.out.println(array[i]); + } // Iterate over the array using a for-each loop and print out each item - + for (String string : array) { + System.out.println(string); + } /* * Reminder! * diff --git a/src/ListPractice.java b/src/ListPractice.java index f4de8e7..e50dce7 100644 --- a/src/ListPractice.java +++ b/src/ListPractice.java @@ -1,28 +1,42 @@ +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("Jameson"); + list.add("Josh"); + list.add("Auberon"); // 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,"Tina"); // Insert a new element at index 0 (the length of the list will change) - + list.add(0, "Susan"); // Check whether the list contains a certain string - + String check = "Jameson"; + if(list.contains(check)){ + System.out.println("List contains " + check); + }else{ + System.out.println("List does not contain " + check); + } // 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 + " is " + 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 i : list) { + System.out.println(i + "\n"); + } /* * Usage tip! * diff --git a/src/MapPractice.java b/src/MapPractice.java index 7ebfeac..de2c6c6 100644 --- a/src/MapPractice.java +++ b/src/MapPractice.java @@ -1,29 +1,48 @@ - +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 map = new HashMap(); // Put 3 different key/value pairs in the Map // (it's OK to do this one-by-one) - + map.put("Jameson", 18); + map.put("Jace", 16); + map.put("Lexie", 17); // Get the value associated with a given key in the Map - + int value = map.get("Jameson"); // Find the size (number of key/value pairs) of the Map - + int size = map.size(); // Replace the value associated with a given key (the size of the Map shoukld not change) - + map.put("Jameson", 19); // Check whether the Map contains a given key - + String testKey = "Jameson"; + if(map.containsKey(testKey)){ + System.out.println("Map contains " + testKey); + }else{ + System.out.println("Map does not contain " + testKey); + } // Check whether the Map contains a given value - + int testValue = 19; + if(map.containsValue(testValue)){ + System.out.println("Map contains " + testValue); + }else{ + System.out.println("Map does not contain " + testValue); + } // Iterate over the keys of the Map, printing each key - + for (String i : map.keySet()) { + System.out.println(i); + } // Iterate over the values of the map, printing each value - + for (int i : map.values()) { + System.out.println(i); + } // Iterate over the entries in the map, printing each key and value - + for (String i : map.keySet()) { + System.out.println("key: " + i + ", value: " + map.get(i)); + } /* * Usage tip! * diff --git a/src/NumberPractice.java b/src/NumberPractice.java index bbec2fe..854da26 100644 --- a/src/NumberPractice.java +++ b/src/NumberPractice.java @@ -1,18 +1,22 @@ public class NumberPractice { public static void main(String args[]) { // Create a float with a negative value and assign it to a variable - + float negativeNum = -0.5f; // 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 - + System.out.println(positiveNum % 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. - + if(positiveNum % 2 == 0){ + System.out.println(positiveNum + " is Even"); + }else{ + System.out.println(positiveNum + " is Odd"); + } // Divide the number by another number using integer division - + System.out.println(positiveNum / 5); /* * Reminder! * diff --git a/src/Person.java b/src/Person.java index 8ab3f95..f87fae4 100644 --- a/src/Person.java +++ b/src/Person.java @@ -6,14 +6,21 @@ 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" // There should NOT be any print statement in this method. @@ -28,26 +35,28 @@ 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 person = new Person("Jameson", 18); // Create another instance of Person with a different name and age and // assign it to a different variable - + Person person2 = new Person("Lexie", 17); // Print the first person - + person.toString(); // Print the second person - + person2.toString(); // Get the name of the first person and store it in a local variable - + String name = person.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 = person.birthYear(2025); // In a separate statement, print the local variable holding the birth year. - + System.out.println(birthyear); /** * Terminology! * @@ -55,12 +64,15 @@ public static void main(String[] args) { * An instance is a specific object made according to that definition. * We use "instance" and "object" to mean the same thing. * - * For example, if there is a Person class, we can make an instance of a specific person: Auberon. + * For example, if there is a Person class, we can make an instance of a + * specific person: Auberon. * - * There can be many instances for the same class. For example: Auberon, Xinting, Baya are all + * There can be many instances for the same class. For example: Auberon, + * Xinting, Baya are all * different instances of the Person class. * - * Each instance has its own instance variables: Auberon's age can be different from Baya's age. + * Each instance has its own instance variables: Auberon's age can be different + * from Baya's age. */ } } diff --git a/src/SetPractice.java b/src/SetPractice.java index d2fc1c9..3e29c2e 100644 --- a/src/SetPractice.java +++ b/src/SetPractice.java @@ -1,18 +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 set = new HashSet<>(); // Add 3 elements to the set // (It's OK to do it one-by-one) - + set.add("Jameson"); + set.add("Jace"); + set.add("Lexie"); // Check whether the Set contains a given String - + String test = "Jameson"; + if(set.contains(test)){ + System.out.println("Set contains " + test); + }else{ + System.out.println("Set does not contain " + test); + } // Remove an element from the Set - + set.remove("Jace"); // Get the size of the Set - + System.out.println(set.size()); // Iterate over the elements of the Set, printing each one on a separate line - + for (String i : set) { + System.out.println(i); + } /* * Warning! * diff --git a/src/StringPractice.java b/src/StringPractice.java index 8d87617..d7fdb45 100644 --- a/src/StringPractice.java +++ b/src/StringPractice.java @@ -1,26 +1,45 @@ +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 word = "Jameson"; // Find the length of the string - + System.out.println(word.length()); // Concatenate (add) two strings together and reassign the result - + word = word + " Farmer"; // Find the value of the character at index 3 - + System.out.println(word.charAt(3)); // Check whether the string contains a given substring (i.e. does the string have "abc" in it?) - + String test = "James"; + if(word.contains(test)){ + System.out.println(word + " contains " + test); + }else{ + System.out.println(word + " does not contain " + test); + } // Iterate over the characters of the string, printing each one on a separate line - + for (int i = 0; i < word.length(); i++) { + System.out.println(word.charAt(i)); + } // Create an ArrayList of Strings and assign it to a variable - + List list = new ArrayList<>(); // Add multiple strings to the List (OK to do one-by-one) - + list.add("Tina"); + list.add("Josh"); + list.add("Auberon"); // 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 combined = String.join(", ", list); + System.out.println(combined); // Check whether two strings are equal - + String test1 = "Jameson"; + String test2 = "James"; + if(test1.equals(test2)){ + System.out.println(test1 + " equals " + test2); + }else{ + System.out.println(test1 + " does not equal " + test2); + } /* * Reminder! *