Understanding Keywords in Java Learning

Study Case Understanding Keywords in Java Learning Michael Kurniawan (2018123456) University of Cincinnati, 2600 Clifton Ave, Cincinnati, OH 45221, United States kurniaml@mail.uc.edu Abstract Java is a technology first introduced by Sun Microsystems in the mid-1990s as a platform for developing and running software on both standalone computers and in network environments. Java is designed so that its applications are portable and can run on various operating systems through the Java Virtual Machine (JVM) mechanism. This paper discusses the basic concepts of Java programming, the characteristics of the language, and its advantages and limitations in the context of technology education in the United States. Keywords: Programming, Java Language, Keywords INTRODUCTION Technological developments, particularly in the field of computers, have grown rapidly and influenced almost all sectors of modern life in the United States. From federal agencies, private companies, large retail chains, to elementary schools, the use of computers and digital systems has become an important part of daily activities. Falling behind in keeping up with technological developments can cause individuals and institutions to lose their competitiveness in various fields. Java, as defined by Sun Microsystems, is a set of technologies that serve to build and run software on both standalone computers and in network environments. The second generation is known as the Java 2 Platform, which runs on an interpreter called the Java Virtual Machine (JVM). The JVM reads the bytecode in .class files, which are direct representations of machine language. This is what makes Java a portable programming language that can be run on various operating systems as long as the platform has a JVM installed. MICHAEL KURNIAWAN 1 Study Case Java Programming Java is a case-sensitive language, so the use of uppercase and lowercase letters must be strictly observed. Java source code does not require a specific format, so all lines of code can be written in a single line as long as the semicolon (;) is placed correctly. However, to support code readability and maintainability, it is recommended to follow a good writing format as shown in various standard programming styles. When learning the structure of Java programs, there are several weaknesses and strengths that need to be understood as the basis of programming. Weaknesses of Java 1. Write Once, Run Anywhere is not entirely consistent Although Java supports portability, there are still some implementation inconsistencies on certain platforms. For example, the SWT-AWT bridge does not run optimally on systems such as the latest macOS. 2. Easy to decompile Java bytecode stores many high-level attributes such as class names, methods, and data types, making it relatively easy to reverse into source code through the decompilation process. The same condition also occurs on the Microsoft .NET platform, making algorithms in applications more difficult to hide and prone to reverse engineering. 3. Relatively large memory usage Java applications typically require more memory than previous generation languages such as C++ or Pascal. This is not a problem for modern devices, but it can be an obstacle on older computers with limited memory capacity. 4. Java Micro Edition implementation is not uniform In the era of J2ME usage, each device vendor often had different modules, so developers had to perform special compilations based on the device model used. Advantages of Java 1. Platform Independent One of Java's main advantages is its ability to run on various operating systems without changing the source code. For example, a Java program created on Windows can be transferred to Linux or macOS without additional modifications, as long as the platform has a JVM. 2. Simple and Object-Oriented MICHAEL KURNIAWAN 2 Study Case Java was designed using concepts from languages such as C and C++, so programmers who understand the basics of those languages will find Java easier to learn. This language eliminates complex features that are considered confusing, making it easier to understand. 3. Automatic Garbage Collection Java provides an automatic memory management mechanism through a garbage collector, so programmers do not need to manage memory allocation manually as in C++. This feature helps reduce memory management errors. 4. Does Not Support Multiple Inheritance To avoid complexity and potential conflicts in class inheritance, Java eliminates the concept of multiple inheritance and replaces it with an interface mechanism. 5. Reducing Pointer Arithmetic To improve security and avoid unauthorized memory access, Java limits the use of pointers by replacing them with a more secure reference system. 6. Extensive Library Java has an extensive standard library, which is continuously developed by the community and major technology companies in the US. This makes it easier for developers to build applications quickly and efficiently. 7. Well-Suited for Large-Scale Applications Because Java is entirely object-based, it facilitates the structured and organized design, development, and debugging of large-scale programs. 8. C++-Like Syntax Java has a syntax similar to C++, so many C++ programmers in the United States have switched to Java. Many universities, including the University of Cincinnati, use Java as one of their introductory programming languages because it is easier for new students to understand and is relevant to various industries. RESULTS AND DISCUSSION Variables in Java Like other programming languages, Java uses variables as containers to store values or data. Java is known as a strongly typed language, which means that each variable must be explicitly declared with its data type. Errors in writing data types or declaration MICHAEL KURNIAWAN 3 Study Case rules will cause errors during the compilation process. Variables function as containers for storing values of a certain type. To define a variable, an identifier or variable name is used to represent the memory location where the value is stored. Identifiers Identifiers are a series of characters used to name variables, methods, classes, interfaces, and packages. Like most modern programming languages, Java has rules regarding valid identifiers. An identifier is considered valid if it begins with: a. An alphabetical letter b. A currency character c. An underscore (_) Furthermore, an identifier can consist of: d. Letters e. Numbers f. Underscores (_) Identifiers cannot contain characters such as @ or spaces, nor can they begin with a number. In addition, identifiers cannot use Java keywords. List of Java Keywords abstract, double, int, strictfp boolean, false, static, super break, extends, long, switch byte, final, native, synchronized case, finally, new, this catch, float, package, throw char, for, private, throws class, goto, protected, transient const, if, public, try continue, implements, return, void default, import, short, volatile do, instanceof, interface, while Java also supports the use of Unicode characters as identifiers. Variable Declaration Basic Syntax [data type] [variable name] MICHAEL KURNIAWAN 4 Study Case Declaration examples: int number; char character; float decimalValue; boolean status; Assigning values is done using the = sign: number = 20; character = ‘k’; decimalValue = 22.2f; status = true; Declaration and initialization can be combined: int number = 20; char character = ‘k’; float decimalValue = 22.2f; boolean status = true; To make a variable constant, use the final keyword: final int constantNumber = 10; final float tax = 15.5f; To make it accessible without creating an object, constants can be added with the public static modifier: public static final int constantNumber = 10; Java Data Types Java data types are divided into two main groups: primitive data types and reference data types.: Primitive Data Types 1. Integer Used for numbers without decimals. The following are the basic integer types: Table 1. Description of Integer Types MICHAEL KURNIAWAN 5 Study Case The int type is used as standard, while byte and short are usually only for memory-saving applications. The long type is used when a very large number capacity is required. 2. Floating Point Used for decimal numbers. The two main types are: Table 2. Description of Floating Point Numbers Notes: • Decimal numbers without a suffix are considered double. • To make it a float, add f or F. 3. Char Char stores one character and is written with single quotes ‘ ’. Char follows the Unicode standard (0–65535), for example: ‘\u1234’ In addition to normal characters, there are special characters: Table 3. Special Characters in Jawa 4. Boolean Boolean has only two values: true and false, and is used for condition evaluation and program flow control. MICHAEL KURNIAWAN 6 Study Case Reference Data Types Consists of objects created from a specific class, such as String, Scanner, or custom objects. Its value is a reference to the object's memory location. Operators in Java Operators are symbols that give instructions to the compiler to perform calculations or data manipulation. Types of operators include arithmetic, increment/decrement, assignment, relational, logical, and bitwise. 1. Arithmetic Operators Table 4. Arithmetic Operators 2. Increment and Decrement Operators Table 5. Increment and Decrement Operators 3. Assignment Operators Table 6. Assignment Operators MICHAEL KURNIAWAN 7 Study Case 4. Relational Operators Table 7. Relational Operators 5. Logical Operators Table 8. Logical Operators 6. Bitwise Operators Table 9. Bitwise Operators MICHAEL KURNIAWAN 8 Study Case 7. Bitwise AND Table 10. Bitwise AND Operations 8. Bitwise OR Table 11. Bitwise OR Operations 9. Bitwise XOR Table 12. Bitwise XOR Operation 10. Bitwise Complement The bitwise complement operation produces bits that are the opposite of the input bits. This means that every bit with a value of 0 will become 1, and every bit with a value of 1 will become 0. The illustration is as follows: Table 13. Bitwise Complement Operation MICHAEL KURNIAWAN 9 Study Case 11. Operator Precedence (Operator Priority) Often, an expression involves multiple operators. Java implements an operator precedence order that determines the execution order of subexpressions. The operator precedence order, from highest to lowest, is summarized as follows: Table 14. Operator Precedence in Jawa Note: these precedence rules determine evaluation, but the use of parentheses () is always recommended to clarify the programmer's intent. Program: True Love Calculator Here is the revised Java code. This code uses Swing for a simple interface. Important improvements made to the code: import import import import import import import import import import java.awt.EventQueue; javax.swing.JFrame; javax.swing.JPanel; javax.swing.border.EmptyBorder; javax.swing.JLabel; javax.swing.JOptionPane; javax.swing.JTextField; javax.swing.JButton; java.awt.event.ActionListener; java.awt.event.ActionEvent; public class TrueLoveCalculator extends JFrame { private JPanel contentPane; private JTextField txtName; private JTextField txtPartner; public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { try { TrueLoveCalculator frame = new TrueLoveCalculator(); frame.setVisible(true); } catch (Exception e) { MICHAEL KURNIAWAN 10 Study Case e.printStackTrace(); } } }); } public TrueLoveCalculator() { setTitle("True Love Calculator"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setBounds(100, 100, 420, 170); contentPane = new JPanel(); contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); setContentPane(contentPane); contentPane.setLayout(null); JLabel lblName = new JLabel("Your Name:"); lblName.setBounds(12, 14, 100, 15); contentPane.add(lblName); JLabel lblPartner = new JLabel("Partner's Name:"); lblPartner.setBounds(12, 50, 120, 15); contentPane.add(lblPartner); txtName = new JTextField(); txtName.setBounds(140, 12, 240, 19); contentPane.add(txtName); txtName.setColumns(10); txtPartner = new JTextField(); txtPartner.setBounds(140, 48, 240, 19); contentPane.add(txtPartner); txtPartner.setColumns(10); JButton btnCalculate = new JButton("Calculate"); btnCalculate.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent arg0) { String name1 = txtName.getText().toLowerCase(); String name2 = txtPartner.getText().toLowerCase(); char[] letters = {'t','r','u','e','l','o','v','e'}; int[] freq = new int[letters.length]; for (int i = 0; i < name1.length(); i++) { for (int j = 0; j < letters.length; j++) { if (name1.charAt(i) == letters[j]) { freq[j]++; } } } for (int i = 0; i < name2.length(); i++) { for (int j = 0; j < letters.length; j++) { if (name2.charAt(i) == letters[j]) { freq[j]++; } } } int True = (freq[0] + (6 * freq[1]) + (15 * freq[2]) + (20 * freq[3]) + (15 * freq[4]) + (6 * freq[5]) + freq[6]) % 10; int Love = (freq[1] + (6 * freq[2]) + (15 * freq[3]) + (20 * freq[4]) + (15 * freq[5]) + (6 * freq[6]) + freq[7]) % 10; MICHAEL KURNIAWAN 11 Study Case int percentage = True * 10 + Love; // combine the two digits JOptionPane.showMessageDialog(null, "Compatibility level: " + percentage + "%"); } }); btnCalculate.setBounds(280, 90, 100, 25); contentPane.add(btnCalculate); } } Important improvements made to the code: • Removed irrelevant text/typos (aliyawb in the previous version). • Combined the two digits of the result (True and Love) into a single percentage value: percentage = True * 10 + Love. • Moved labels and variable names to English to match the US context (the UI can still be changed back as needed). • Maintained the Swing structure so that the program can be compiled and run directly. Program Results The simple program above generates a compatibility score (percentage) based on the occurrence of letters in the two names entered. The value displayed consists of two digits formed from the numbers True (tens) and Love (units), so the sample output could be 73%, 42%, and so on. Figure 1. True Love Calculator application display (example of Swing interface). MICHAEL KURNIAWAN 12 Study Case CONCLUSION Based on the discussion, it can be concluded that Java is a strongly typed programming language—each variable must be declared with its data type; negligence in the declaration will cause an error during compilation. The Java data type structure is not much different from other languages such as C, C++, Pascal, and BASIC, which include integer, floating point, char, and boolean. The rules for naming variables are also commonly found in other programming languages: they must begin with a letter/alphabet, currency character, or underscore (_), and can contain letters, numbers, and underscores; they cannot use the language's built-in keywords. In addition to arithmetic operators, Java provides increment/decrement, assignment, relational, logical, and bitwise (AND, OR, XOR, complement) operators, as well as operator precedence rules that must be understood in order to write correct and predictable expressions. As a contextual note: Java is widely taught in universities in the United States as an introductory language because its syntax is familiar to C/C++ programmers and it is applicable for large-scale software development. REFERENCE MICHAEL KURNIAWAN 13 Study Case MICHAEL KURNIAWAN 14