Computer Programming-2: Introduction to Java
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Questions and Answers

Which characteristic of Java allows it to run on any correctly implemented Java system?

  • Platform independence (correct)
  • Object-oriented programming
  • Embedded in web pages
  • Rich collection of packages

Java is only designed for use in desktop applications.

False (B)

Name one predefined class in Java that is commonly used for input and output operations.

JOptionPane

Java is structured in terms of __________, which group data with operations on that data.

<p>classes</p> Signup and view all the answers

Match the following Java features with their definitions:

<p>Primitive data types = Basic types of data for variable storage Control structures = Direct the flow of execution in programs Object-oriented programming = Concept of structuring code into classes Packages = Collections of related classes and interfaces</p> Signup and view all the answers

What keyword indicates a static method in Java?

<p>static (B)</p> Signup and view all the answers

Java methods can modify the value of the caller's primitive type arguments.

<p>False (B)</p> Signup and view all the answers

What type of method is referred to as an instance method?

<p>A method that is not static.</p> Signup and view all the answers

In Java, all method arguments are passed by __________.

<p>value</p> Signup and view all the answers

Match the following types of method arguments with their characteristics:

<p>Primitive type = Value is copied to the method Object reference = Address of the object is passed Static method = Belongs to the class Instance method = Belongs to an instance of the class</p> Signup and view all the answers

What does a Java source code compiler produce?

<p>Java byte code (D)</p> Signup and view all the answers

A Java class must be defined in a file whose name matches the class name.

<p>True (A)</p> Signup and view all the answers

What is the role of a Java Virtual Machine?

<p>To load and execute class files.</p> Signup and view all the answers

A class describes ________ having common characteristics.

<p>objects</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Class = Unit of programming describing objects Byte Code = Output of the Java compiler Java Virtual Machine = Executes Java class files Data Fields = Hold attributes of objects</p> Signup and view all the answers

What characteristic of a class provides operations that can be performed on objects?

<p>Methods (C)</p> Signup and view all the answers

Java programs can consist of only one class.

<p>False (B)</p> Signup and view all the answers

What is produced by compiling a Java source code file?

<p>A .class file containing Java byte code.</p> Signup and view all the answers

Which of the following operators are used for logical or relational operations in Java?

<p>&amp;&amp; (A), == (D)</p> Signup and view all the answers

In Java, the operator '>>>' represents a signed shift operation.

<p>False (B)</p> Signup and view all the answers

What does the 'API' in Java stand for?

<p>Application Programming Interface (C)</p> Signup and view all the answers

What is a widening conversion in Java?

<p>A widening conversion is when a numeric type of smaller range is converted to a numeric type of larger range in mixed-type operations or assignments.</p> Signup and view all the answers

When converting a byte to a larger numeric type, the correct order is byte, _____, int, long.

<p>short</p> Signup and view all the answers

The main method in Java is the entry point for execution of a program.

<p>True (A)</p> Signup and view all the answers

What package would you import to use classes for graphical user interface in Java?

<p>javax.swing</p> Signup and view all the answers

Match the following Java operators with their function:

<p>== = Equality Comparison &amp;&amp; = Logical AND</p> <ul> <li>= Addition or String Concatenation ~ = Bitwise Complement</li> </ul> Signup and view all the answers

In Java, an _______ statement tells the compiler to make available classes and methods of another package.

<p>import</p> Signup and view all the answers

Which operator is used for conditional expressions in Java?

<p>? (D)</p> Signup and view all the answers

The operator 'new' in Java is used for object creation.

<p>True (A)</p> Signup and view all the answers

What is the result of the command 'javac HelloWorld.java'?

<p>It compiles HelloWorld.java into HelloWorld.class. (A)</p> Signup and view all the answers

Match the Java packages with their descriptions:

<p>Swing = GUI package AWT = Application Window Toolkit util = Utility data structures main = Entry point of a Java program</p> Signup and view all the answers

What is the role of the assignment operator '=' in Java?

<p>The assignment operator '=' is used to assign values to variables.</p> Signup and view all the answers

The keyword 'static' in Java implies that a method is part of an object.

<p>False (B)</p> Signup and view all the answers

What does the command 'java HelloWorld' do?

<p>Runs the main method of the HelloWorld class.</p> Signup and view all the answers

Which of the following is NOT a primitive data type in Java?

<p>String (C)</p> Signup and view all the answers

The boolean data type can hold more than two values.

<p>False (B)</p> Signup and view all the answers

What is the range of values for a short data type?

<p>-32,768 to 32,767</p> Signup and view all the answers

The ______ data type in Java is used to represent characters.

<p>char</p> Signup and view all the answers

What is the range of values for a long data type?

<p>-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (C)</p> Signup and view all the answers

The float data type in Java can represent very large numbers, but has approximately 15 digits of precision.

<p>False (B)</p> Signup and view all the answers

Which primitive data type is used for true/false values?

<p>boolean</p> Signup and view all the answers

Match the following Java primitive data types with their descriptions:

<p>byte = 8 bits, -128 to 127 double = 64 bits, about 15 digits precision char = Represents a single Unicode character int = 32 bits, -2,147,483,648 to 2,147,483,647</p> Signup and view all the answers

Flashcards

Java platform independence

Java programs can run on any system with a correctly implemented Java environment, without needing changes.

Object-Oriented Programming (OOP) in Java

Java organizes code using classes. Classes combine data (attributes) and actions (methods) related to that data.

Java Primitive Data Types

Fundamental data types used in Java, like int, double, boolean for storing numbers, decimals, and true/false values.

Java Control Structures

Structures like if-else, for, while that control the flow of execution in a Java program.

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Java Packages

Collections of classes in Java to perform common tasks.

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Java Source Code

Text files with Java programming instructions.

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Bytecode

The output of a Java compiler, platform-independent instructions.

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Java Compiler

Transforms Java source code into bytecode.

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Class File

A file containing bytecode for a Java class.

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Java Virtual Machine (JVM)

The runtime environment that executes Java bytecode.

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Class

A blueprint for creating objects with shared data and methods.

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Object (instance)

A specific realization of a class, having properties and behaviours.

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Data Fields

Variables that hold the data values associated with an object.

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Java API

Application Programming Interface; a large collection of packages within Java.

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Java Package

A group of related Java classes.

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Swing Package

Java GUI package for creating graphical user interfaces (GUIs).

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AWT Package

Another Java GUI package (older than Swing).

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util Package

Contains essential utility data structures and classes needed in programs.

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import statement

Makes classes and methods of another package available in your code.

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main method

The entry point for a Java program, specifying where execution begins.

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javac command

Compiles Java source code to bytecode.

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Primitive Types (Java)

Basic data types in Java like integers, floating-point numbers, and characters directly stored in memory.

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Reference Variables

Variables that store memory addresses of objects, not the objects themselves.

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Integer Data Types (Java)

Java data types used to represent whole numbers: byte, short, int, and long, each with a different size and range.

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Floating-Point Types (Java)

Java's float and double types for representing real numbers with decimal points, with varying precision.

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Character Type (Java)

The 'char' data type used for representing single Unicode characters.

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Boolean Type (Java)

The 'boolean' data type that can hold only true or false values.

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Data Type Range (byte)

The range of values that can be stored in a byte data type in Java, from -128 to 127.

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Data Type Range (int)

The range of values that an int type can hold in java from -2,147,483,648 to 2,147,483,647.

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Java Method

A block of code in Java that performs a specific task.

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Static Method

A method that belongs to the class, not a specific object of the class.

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Instance Method

A method associated with an object of a class.

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Call-by-value (Primitives)

When passing a primitive type to a method, a copy of the value is made, not the original.

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Call-by-value (Objects)

When passing an object to a method, a copy of the reference to the object is made, not the object itself.

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Operator Types

Different symbols used in Java for operations like arithmetic, comparison, and assignment.

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Widening Conversions

Converting a smaller data type to a larger one in Java, e.g., int to double.

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Mixed-Type Operands

Combining variables of different data types in a Java expression.

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Assignment Operators

Symbols like = and += used to assign values to variables in Java.

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Comparison Operators

Operators like < and >= that compare values, returning a boolean result (true/false).

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Arithmetic Operators

Symbols that perform mathematical operations like addition, subtraction, multiplication, division in Java.

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Sequential Logical Operators

Operators like && (and) and || (or) that evaluate boolean expressions and return a boolean value.

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Data Type Conversion

Changing a value from one data type to another in Java - such as from int to float or float to double.

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Study Notes

Computer Programming-2, Lecture 1

  • The lecture is about Java Programming
  • The course material is from Liang's "Introduction to Java Programming" Eighth Edition, copyright 2011
  • The textbook ISBN is 0132130807

Introduction to Java

  • This section introduces Java

Topics of the Review

  • Essentials of object-oriented programming in Java
  • Java primitive data types, control structures, and arrays
  • Predefined classes: Math, JOptionPane, I/O streams, String, StringBuffer, StringBuilder, StringTokenizer
  • Writing and documenting your own Java classes

Some Salient Characteristics of Java

  • Java is platform-independent; the same program runs on any correctly implemented Java system
  • Java is object-oriented
    • Structured in terms of classes that group data with operations on that data
    • Constructs new classes by extending existing ones
  • Java is designed as a core language plus a rich collection of commonly available packages
  • Java can be embedded in web pages

Java Processing and Execution

  • Begin with Java source code in text files (e.g., Model.java)
  • A Java source code compiler produces Java byte code (outputs one file per class: Model.class)
  • A Java Virtual Machine loads and executes class files; may compile to native code (e.g., x86) internally

Compiling and Executing a Java Program

  • Java source files are compiled to bytecode
  • The bytecode is then run by the Java Virtual Machine (JVM)

Classes and Objects

  • The class is the unit of programming
  • A Java program is a collection of classes
  • Each class definition is usually in its own .java file. File name matches class name
  • A class describes objects (instances)
    • Describes their common characteristics (a blueprint)
    • All instances have these same characteristics
  • Characteristics include data fields and methods (operations)

Grouping Classes: The Java API

  • API = Application Programming Interface
  • Java is a small core with an extensive collection of packages
  • Packages consist of related Java classes
    • Swing: GUI package
    • AWT: Application Window Toolkit (more GUI)
    • util: utility data structures (important to CS 187!)
  • Import statement makes classes and methods available from another package
  • A main method indicates where execution of a program begins

A Little Example of import and main

  • import javax.swing.*;
  • public class HelloWorld
  • public static void main(String[] args)
  • public = can be seen from any package
  • static = not part of an object

Processing and Running HelloWorld

  • javac HelloWorld.java (produces the HelloWorld.class file)
  • java HelloWorld (runs the program)

References and Primitive Data Types

  • Java distinguishes primitive types and objects
  • Primitive-type data is stored in primitive-type variables
  • Reference variables store the address of an object
  • No notion of "object physically in the stack" or "object physically within an object"

Primitive Data Types

  • Represent numbers, characters, Boolean values
  • Integers: byte, short, int, long
  • Real numbers: float, double
  • Characters: char

Primitive Data Types (continued)

  • Table with data type and range of values (e.g., byte: -128 to 127)

Primitive Data Types (continued- table)

  • Shows first 128 Unicode symbols

Operators

  • Summary of operators in Java

Operators (continued)

  • Summary of operators in Java (logical, conditional, assignment)

Type Compatibility and Conversion

  • Widening conversion: In operations on mixed-type operands, the numeric type of the smaller range is converted to the numeric type of the larger range. Also in assignments
  • byte to short to int to long; int to float to double

Declaring and Setting Variables

  • Declaring int square; square = n * n;
  • Declaring double cube = n*(double)square;
  • Variables get a safe initial value (zero/null)

Referencing and Creating Objects

  • Declaring reference variables (they reference objects of specified types)
  • Two reference variables can reference the same object
  • The new operator creates an instance of a class
  • A constructor executes when a new object is created
  • Example: String greeting = "hello";

Java Control Statements

  • A group of statements executes in order
  • Control statements alter the sequential flow of execution

Java Control Statements (continued)

  • Table with various control structures (if/else, switch, while, for, do-while); their purposes, and syntax

Methods

  • A Java method defines a group of statements as performing a particular operation,
  • static indicates a static or class method
  • Method arguments are passed call-by-value

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Computer Programming-2 Lecture 1 PDF

Description

This quiz covers the foundational concepts of Java programming as outlined in Liang's 'Introduction to Java Programming'. Topics include object-oriented programming essentials, Java data types, control structures, and predefined classes. Get ready to test your knowledge on writing and documenting Java classes!

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