1.1 Why Programming? Why Java?

Part I

Enduring Understanding

Some objects or concepts are so frequently represented that programmers can draw upon existing code that has already been tested, enabling them to write solutions more quickly and with a greater degree of confidence.

Learning Objective

Call System class methods to generate output to the console.

Essential Knowledge

• System.out.print and System.out.println display information on the computer monitor.

• System.out.println moves the cursor to a new line after the information has been displayed, while System.out.print does not.

Introduction

There are several reasons why learning Java is beneficial:

1. Popularity and widespread use: Java is one of the most popular programming languages in the world. It is used extensively in a variety of domains, including web development, mobile app development, enterprise software, scientific applications, and more. By learning Java, you increase your chances of finding job opportunities and collaborating on various projects.

2. Platform independence: Java programs can run on any platform that has a Java Virtual Machine (JVM) installed. This "write once, run anywhere" capability makes Java a versatile language, enabling you to develop applications that can be deployed on different operating systems, such as Windows, macOS, Linux, and more.

3. Object-oriented programming (OOP): Java is an object-oriented programming language, which means it allows you to organize your code into reusable objects. OOP promotes modular and structured programming, making it easier to maintain and update codebases. Understanding and applying OOP principles through Java can improve your overall programming skills and prepare you for learning other languages.

4. Robust and mature ecosystem: Java has been around for several decades and has a vast ecosystem of libraries, frameworks, and tools. This rich set of resources can significantly speed up the development process and help you build complex applications more efficiently. Whether you need to create a web application using frameworks like Spring or develop an Android app with Android Studio, Java offers a wide range of tools and resources to support your development needs.

5. Career opportunities: Java skills are in high demand in the job market. Many companies and organizations actively seek Java developers due to the language's popularity and its extensive use in various industries. Learning Java can open up opportunities for software development positions, ranging from entry-level to senior roles, across different sectors.

Overall, learning Java can equip you with a powerful and versatile programming language, increasing your employability, broadening your development opportunities, and providing a solid foundation for your programming career.

System.out.println

In Java, System.out.println and System.out.print are methods provided by the java.lang.System class for printing output to the console.

• The println method is used to print a line of text to the console.

• It takes one or more arguments, which can be literals (hard-coded values) or variables, and displays them as text followed by a newline character.

Example

Example_1_1_1.java

public class Example_1_1_1
{
    public static void main(String[] args)
    {
        System.out.println("Example 1.1.1");
        System.out.println("Hello World!");
    }
}

Output

Example 1
Hello World!

System.out.print

• The print method is similar to println, but it does not add a newline character at the end of the output. Hence, the next output will be displayed on the same line.

• It takes the same type of arguments as println.

Example

Example_1_1_2.java

public class Example_1_1_2
{
    public static void main(String[] args)
    {
        System.out.println("Example 1.1.2");
        System.out.print("Hello ");
        System.out.print("World ");
        System.out.print("again!!");
    }
}

Output

Example 2
Hello World again!!

Both println and print can be used to display different types of data, including strings, numbers, variables, and expressions. They are often used for debugging, displaying intermediate results, or providing information to the user during program execution.

Part II

Enduring Understanding

To find specific solutions to generalizable problems, programmers include variables in their code so that the same algorithm runs using different input values.

Learning Objective

Create string literals.

Essential Knowledge

A string literal is enclosed in double quotes.

Introduction

In Java, a string literal is a sequence of characters enclosed in double quotation marks ("). It is a way to represent a fixed sequence of characters, such as words, sentences, or even empty strings.

String literals in Java have some important characteristics:

1. Immutable: Once a string literal is defined, its value cannot be changed. Java strings are immutable, meaning you cannot modify the characters within a string directly. Instead, operations on strings usually return new strings.

2. Concatenation: String literals can be concatenated using the + operator. This results in a new string that is the concatenation of the original strings. For example: "Hello, " + "World!"

3. Escape Sequences: String literals can contain special escape sequences, which are combinations of characters used to represent certain characters or control characters. For example, \n represents a newline character, \t represents a tab character, \" represents a double quotation mark, and \\ represents a backslash. Escape sequences allow you to include characters that would otherwise be challenging to represent directly in a string literal.

4. Unicode Support: Java string literals support Unicode characters. You can use Unicode escape sequences to represent characters using their hexadecimal Unicode code points. For example, "\u03B1" represents the Greek letter alpha (α).

String literals are widely used in Java for representing text-based data, such as messages, names, file paths, and more. They are fundamental in many aspects of Java programming, including input/output operations, manipulating text, and working with APIs and libraries that deal with textual data.

Note, a string literal in Java must be enclosed in double quotation marks ("), not single quotes ('). Single quotes are used to represent character literals in Java.

For example, the following is a valid character literal in Java: 'A'

The single quotation marks indicate that 'A' represents a single character, not a string.

Example

Example_1_1_3.java

public class Example_1_1_3
{
    public static void main(String[] args)
    {
        System.out.println("Example 1.1.3");
        System.out.println("\n");
        System.out.println("\u03B1");
        System.out.println("😀😂😇");
    }
}

Output

Example 3


α
😀😂😇