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Table of Contents

Vocab
Code Examples

Notebook Style Guide

Vocab

Basics

algorithm

Definition: A step-by-step process used to complete a task or solve a problem.

Java example:

int total = price1 + price2;
System.out.println(total);
sequencing

Definition: The order in which instructions are completed. Changing the order can change the result.

variable

Definition: A named storage location that holds a value that can change.

Java example:

int score = 10;
score = 15;
variable declaration

Definition: Creating a variable by giving Java its data type and name.

Structure / syntax:

dataType variableName;

Java example:

String weather;
variable initialization

Definition: Giving a variable its first value when it is created.

Structure / syntax:

dataType variableName = value;

Java example:

String weather = "sunny";
assignment

Definition: Using = to store or replace a value in a variable.

Java example:

weather = "rainy";
data types

Definition: Categories that tell Java what kind of value a variable can store.

Java example:

String name = "Alex";
int age = 16;
double height = 5.8;
boolean hasPermit = true;
String

Definition: A Java type used to store text.

Java example:

String playerName = "Alex";
int

Definition: A Java type used to store whole numbers.

Java example:

int lives = 3;
double

Definition: A Java type used to store numbers that may contain decimals.

Java example:

double price = 12.99;
boolean

Definition: A Java type that stores only true or false.

Java example:

boolean isLoggedIn = false;
console / output

Definition: The console displays information produced by a program. Information sent out by a program is output.

Java example:

System.out.println("Hello World!");
concatenation

Definition: Combining Strings together with the + operator.

Java example:

String fullName = firstName + " " + lastName;
type conversion / casting

Definition: Changing a value from one data type to another.

Java example:

int age = Integer.parseInt("16");
double price = 19.99;
int wholePrice = (int) price;

Casting a double to an int removes the decimal portion; it does not round.

Methods

method

Definition: A reusable block of code that performs a task.

Java example:

static void sayHi() {
    System.out.println("Hi!");
}
method declaration

Definition: The code that defines a method's name, return type, parameters, and body.

Java example:

static void greet(String name) {
    System.out.println("Hello, " + name);
}
method call

Definition: An instruction that tells Java to run a method.

Java example:

greet("Jordan");
parameter

Definition: A variable listed in a method declaration that receives information.

Java example:

static void greet(String name) {
    System.out.println("Hello, " + name);
}
argument

Definition: A value supplied to a method when it is called.

Java example:

greet("Jordan");
void

Definition: A method return type that means the method does not send a value back.

Java example:

static void printMessage() {
    System.out.println("Hello");
}
return type

Definition: The data type written before a method name that tells Java what type of value the method returns.

Java example:

static int getScore() {
    return 100;
}
return statement

Definition: Sends a value back from a method and ends that method.

Java example:

static int add(int a, int b) {
    return a + b;
}
scope / local variable

Definition: Scope is where a name can be used. A local variable exists only inside the method or block where it is declared.

Java example:

static void example() {
    int score = 10;
    System.out.println(score);
}
// score cannot be used here
method overloading

Definition: Creating multiple methods with the same name but different parameter lists.

Java example:

static void show(int number) { }
static void show(String text) { }

User Input

Scanner

Definition: A Java class commonly used to read keyboard input.

Java example:

import java.util.Scanner;

Scanner input = new Scanner(System.in);
user input

Definition: Information entered into a program by the user while the program is running.

Java example:

System.out.print("Enter your age: ");
int age = input.nextInt();
Scanner input methods

Definition: Methods used to read different kinds of input with a Scanner.

Java example:

String name = input.nextLine();
int age = input.nextInt();
double price = input.nextDouble();

nextLine() reads text, nextInt() reads an integer, and nextDouble() reads a decimal number.

Operators

arithmetic operators

Definition: Operators used for math: +, -, *, and /.

Java example:

int total = 5 + 2;
int product = 5 * 2;
double quotient = 5.0 / 2.0;
modulus (%)

Definition: Returns the remainder after division.

Java example:

System.out.println(10 % 3); // 1
increment / decrement

Definition: ++ increases by 1. -- decreases by 1.

Java example:

score++;
lives--;
compound assignment

Definition: Combines an operation with assignment, such as +=, -=, *=, and /=.

Java example:

score += 5;
health -= 10;
comparison operators

Definition: Compare two values and produce true or false: ==, !=, <, >, <=, >=.

Java example:

System.out.println(score >= 70);
System.out.println(lives != 0);

Control Structures

conditional statement

Definition: A statement that makes a decision based on a boolean condition.

Java example:

if (temperature < 50) {
    System.out.println("Wear a jacket.");
}
if statement

Definition: Runs a block of code only when its condition is true.

Java example:

if (score >= 90) {
    System.out.println("A");
}
if / else

Definition: Chooses between two paths.

Java example:

if (age >= 18) {
    System.out.println("Adult");
} else {
    System.out.println("Minor");
}
if / else if / else

Definition: Checks multiple conditions in order and runs the first matching branch.

Java example:

if (score >= 90) {
    System.out.println("A");
} else if (score >= 80) {
    System.out.println("B");
} else {
    System.out.println("Below B");
}
nested if statement

Definition: An if statement placed inside another conditional statement.

Java example:

if (age >= 16) {
    if (hasPermit) {
        System.out.println("Can practice driving");
    }
}
logical operators

Definition: Operators used with booleans: && means AND, || means OR, and ! means NOT.

Java example:

boolean canDrive = age >= 16 && hasPermit;
boolean canEnter = hasID || hasPass;
boolean unlocked = !isLocked;
compound boolean expression

Definition: A boolean expression made by combining two or more conditions.

Java example:

boolean eligible = age >= 16 && hasPermit;
De Morgan's Law

Definition: Rules for rewriting negated compound boolean expressions.

Java example:

!(A && B)  // same as !A || !B
!(A || B)  // same as !A && !B
for loop

Definition: A loop commonly used when initialization, condition, and update can be written together.

Structure / syntax:

for (initialization; condition; update) {
    // repeated code
}

Java example:

for (int i = 0; i < 5; i++) {
    System.out.println(i);
}
while loop

Definition: A loop that repeats while its condition remains true.

Java example:

int count = 0;
while (count < 5) {
    System.out.println(count);
    count++;
}
infinite loop

Definition: A loop that never stops because its condition never becomes false.

Java example:

int count = 0;
while (count < 5) {
    System.out.println(count);
    // count never changes
}

Classes and Objects

class

Definition: A blueprint that describes the data and behaviors objects of that type can have.

Java example:

public class Friend {

}
object

Definition: A specific object created from a class.

Java example:

Friend jasmine = new Friend("Jasmine", 15);
instance

Definition: Another name for an object created from a class.

Java example:

Friend jasmine = new Friend("Jasmine", 15);
instance field

Definition: A variable declared in a class that stores information for each object.

Java example:

public class Friend {
    String name;
    int age;
}
constructor

Definition: A special part of a class that runs when a new object is created and usually gives it starting values.

Structure / syntax:

public ClassName(parameters) {
    // setup code
}

Java example:

public Friend(String friendName, int friendAge) {
    name = friendName;
    age = friendAge;
}
constructor parameter

Definition: A parameter in a constructor that receives a value when a new object is created.

Java example:

public Friend(String friendName, int friendAge) {
    name = friendName;
    age = friendAge;
}
new keyword

Definition: The keyword used to create a new object from a class.

Java example:

Friend jasmine = new Friend("Jasmine", 15);
dot notation

Definition: Using a dot after an object name to access one of its fields or methods.

Java example:

System.out.println(jasmine.name);
jasmine.greeting();
static vs. non-static methods

Definition: A static method belongs to the class. A non-static method belongs to an object and can directly use that object's instance fields.

Java example:

static void classMessage() {
    System.out.println("Class method");
}

void greeting() {
    System.out.println("Hello, " + name);
}
abstraction

Definition: Using a simpler name or interface without handling all internal details every time.

Java example:

Friend jasmine = new Friend("Jasmine", 15);
System.out.println(jasmine.name);

Useful Java Tools

Math class

Definition: A built-in Java class containing useful static math methods and constants.

Java example:

double root = Math.sqrt(25);
double power = Math.pow(2, 3);
double absolute = Math.abs(-7);
Math.random()

Definition: Returns a random double from 0.0 up to, but not including, 1.0.

Java example:

int randomNumber = (int) (Math.random() * 10) + 1;

This example creates a random integer from 1 through 10.

Code Examples

Starter Program Example

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

Variables and Updating Values Example

int score = 10;
score = 15;
System.out.println(score);

Strings and Concatenation Example

String firstName = "Dev";
String lastName = "Cat";
System.out.println(firstName + " " + lastName);

User Input Example

import java.util.Scanner;

Scanner input = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = input.nextLine();

Comparison Operators Example

int score = 85;
System.out.println(score == 85);
System.out.println(score != 100);
System.out.println(score >= 70);

If Statement Example

if (score >= 90) {
    System.out.println("A");
}

If / Else Example

if (age >= 18) {
    System.out.println("Adult");
} else {
    System.out.println("Minor");
}

If / Else If / Else Example

if (score >= 90) {
    System.out.println("A");
} else if (score >= 80) {
    System.out.println("B");
} else {
    System.out.println("Below B");
}

Compound Booleans Example

boolean canDrive = age >= 16 && hasPermit;
boolean canEnter = hasID || hasPass;
boolean lockedOut = !hasAccess;

De Morgan’s Law Example

!(A && B)   // same as !A || !B
!(A || B)   // same as !A && !B

For Loop Example

for (int i = 0; i < 5; i++) {
    System.out.println(i);
}

While Loop Example

int count = 0;
while (count < 5) {
    System.out.println(count);
    count++;
}

Arithmetic and Modulus Example

int total = 7 + 3;
int product = 7 * 3;
int remainder = 10 % 3;

Method with Parameters Example

static void greet(String name) {
    System.out.println("Hello, " + name);
}

greet("Jordan");

Method that Returns a Value Example

static int add(int a, int b) {
    return a + b;
}

int total = add(4, 6);

Scope Example

static void example() {
    int score = 10;
}
// score cannot be used here

Method Overloading Example

static void show(int number) { }
static void show(String text) { }

Class with Instance Fields Example

public class Friend {
    String name;
    int age;
}

Constructor and Object Creation Example

public class Friend {
    String name;
    int age;

    public Friend(String friendName, int friendAge) {
        name = friendName;
        age = friendAge;
    }

    public static void main(String[] args) {
        Friend jasmine = new Friend("Jasmine", 15);
    }
}

Dot Notation and Non-Static Method Example

public void greeting() {
    System.out.println("Hello, " + name);
}

Friend jasmine = new Friend("Jasmine", 15);
System.out.println(jasmine.name);
jasmine.greeting();

Notebook Style Guide

Keep your notebook useful for you. Add examples, corrections, and notes as you learn.

```java
System.out.println("Hello World!");
```

Bottom Line

Definitions tell you what something means. Code examples show you how to use it. Your notebook should have both. `````