From 46cf215bc1746687e41daf9e23d8397e86ed0c06 Mon Sep 17 00:00:00 2001 From: Stefanurkal Date: Tue, 21 Jan 2025 01:01:55 -0800 Subject: [PATCH] completed all practice items --- src/ArrayPractice.java | 21 +++++++++++++++------ src/ListPractice.java | 26 ++++++++++++++++++++++---- src/MapPractice.java | 31 ++++++++++++++++++++----------- src/NumberPractice.java | 16 +++++++++++----- src/Person.java | 33 +++++++++++++++++++++++---------- src/SetPractice.java | 19 +++++++++++++------ src/StringPractice.java | 28 ++++++++++++++++++---------- 7 files changed, 122 insertions(+), 52 deletions(-) diff --git a/src/ArrayPractice.java b/src/ArrayPractice.java index bc58c83..ccc1471 100644 --- a/src/ArrayPractice.java +++ b/src/ArrayPractice.java @@ -1,18 +1,27 @@ 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] = "Seahawks"; + array[1] = "49ers"; + array[2] = "Rams"; + array[3] = "Cardinals"; // Get the value of the array at index 2 - + String index2 = array[2]; + System.out.println("value at array[2]: " + index2); // Get the length of the array - + int lengthOfArray = array.length; + System.out.println("length of the array is: " + lengthOfArray); // 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 item : array){ + System.out.println(item); + } /* * Reminder! * diff --git a/src/ListPractice.java b/src/ListPractice.java index f4de8e7..9e0591a 100644 --- a/src/ListPractice.java +++ b/src/ListPractice.java @@ -1,28 +1,46 @@ +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 list = new ArrayList<>(); + + // Add 3 elements to the list (OK to do one-by-one) + list.add("Sonics"); + list.add("Mariners"); + list.add("Seahawks"); // Print the element at index 1 + System.out.println("Element at index 1: " + 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, "Sounders"); // Insert a new element at index 0 (the length of the list will change) + list.add(0, "Kraken"); // Check whether the list contains a certain string - + boolean doesContain = list.contains("Sonics"); + System.out.println(doesContain); // 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 - + for (String item : list) { + System.out.println(item); + } /* * Usage tip! * diff --git a/src/MapPractice.java b/src/MapPractice.java index 7ebfeac..bb1bea0 100644 --- a/src/MapPractice.java +++ b/src/MapPractice.java @@ -1,29 +1,38 @@ - +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("Gary", 20); + map.put("Shawn", 40); + map.put("Detlef", 11); // Get the value associated with a given key in the Map - + System.out.println(map.get("Gary")); // Find the size (number of key/value pairs) of the Map - + System.out.println(map.size()); // Replace the value associated with a given key (the size of the Map shoukld not change) - + map.put("Shawn", 4); // Check whether the Map contains a given key - + System.out.println(map.containsKey("Sam")); // Check whether the Map contains a given value - + System.out.println(map.containsValue(33)); // 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 (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..504a080 100644 --- a/src/NumberPractice.java +++ b/src/NumberPractice.java @@ -1,18 +1,24 @@ public class NumberPractice { public static void main(String args[]) { // Create a float with a negative value and assign it to a variable - + float negativeFloat = -3.23f; // Create an int with a positive value and assign it to a variable - + int positiveInt = 11; // Use the modulo % operator to find the remainder when the int is divided by 3 - + int remainder = positiveInt % 3; + System.out.println(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 (positiveInt % 2 == 0) { + System.out.println("Even"); + } else { + System.out.println("Odd"); + } // Divide the number by another number using integer division - + int divisionNum = positiveInt / 5; + System.out.println(divisionNum); /* * Reminder! * diff --git a/src/Person.java b/src/Person.java index 8ab3f95..629a859 100644 --- a/src/Person.java +++ b/src/Person.java @@ -6,14 +6,19 @@ 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 +33,34 @@ public class Person { * @return The year the person was born */ // (create the instance method here) - + public int birthYear(int currentYear) { + int year = currentYear - age; + + return year; + } public static void main(String[] args) { // Create an instance of Person + Person newPerson = new Person("Stephen", 39); + // Create another instance of Person with a different name and age and // assign it to a different variable - // Print the first person + Person anotherPerson = new Person("Max", 12); + // Print the first person + System.out.println(newPerson); // Print the second person - + System.out.println(anotherPerson); // Get the name of the first person and store it in a local variable - + String firstName = newPerson.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 = newPerson.birthYear(2025); // In a separate statement, print the local variable holding the birth year. - + System.out.println(birthYear); /** * Terminology! * diff --git a/src/SetPractice.java b/src/SetPractice.java index d2fc1c9..132c787 100644 --- a/src/SetPractice.java +++ b/src/SetPractice.java @@ -1,18 +1,25 @@ +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 newSet = new HashSet<>(); // Add 3 elements to the set // (It's OK to do it one-by-one) - + newSet.add("Sonics"); + newSet.add("Mariners"); + newSet.add("Seahawks"); // Check whether the Set contains a given String - + System.out.println(newSet.contains("sounders")); // Remove an element from the Set - + newSet.remove("Sonics"); // Get the size of the Set - + System.out.println(newSet.size()); // Iterate over the elements of the Set, printing each one on a separate line - + for (String teams : newSet){ + System.out.println(teams); + } /* * Warning! * diff --git a/src/StringPractice.java b/src/StringPractice.java index 8d87617..21d10b5 100644 --- a/src/StringPractice.java +++ b/src/StringPractice.java @@ -1,26 +1,34 @@ +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 newString = "football"; // Find the length of the string - + int length = newString.length(); + System.out.println(length); // Concatenate (add) two strings together and reassign the result - + String comboString = newString + " season"; // Find the value of the character at index 3 - + char indexChar = comboString.charAt(3); // Check whether the string contains a given substring (i.e. does the string have "abc" in it?) - + boolean containsString = comboString.contains("basketball"); // Iterate over the characters of the string, printing each one on a separate line - + for (int i = 0; i < comboString.length(); i++) { + System.out.println(comboString.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("Seahawks"); + stringList.add("Mariners"); + stringList.add("Sonics"); // 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 joined = String.join(", ", stringList); + System.out.println(joined); // Check whether two strings are equal - + boolean theSame = newString.equals(comboString); /* * Reminder! *