String Methods in Programming
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Questions and Answers

What does the length method return when invoked on a string object?

  • The number of characters in the string (correct)
  • The last character of the string
  • A boolean indicating if the string is empty
  • The first character of the string

    • Which method does NOT return a value when called?

  • println (correct)
  • length
  • charAt
  • toUpperCase

    • How can you utilize the value returned by the length method?

  • By printing it directly without any variable
  • By storing it in a variable for later use
  • By passing it as an argument to another method
  • All of the above (correct)

    • If a string variable 'greeting' contains 'Hello', what will the expression 'greeting.length()' evaluate to?

    <p>5</p> Signup and view all the answers

    What is required for the length method to operate properly?

    <p>The string must be an object</p> Signup and view all the answers

    Which of the following describes a method that both computes and returns a value?

    <p>length method</p> Signup and view all the answers

    What is the output of 'System.out.println(greeting.length());' if 'greeting' contains 'Goodbye'?

    <p>6</p> Signup and view all the answers

    What is a primary purpose of using comments in code?

    <p>To provide explanations for humans who read the code.</p> Signup and view all the answers

    Which statement is true regarding the assignment operator (=)?

    <p>It can change the value of a variable to a new one.</p> Signup and view all the answers

    Which component interacts with the operating system to display output without returning a value?

    <p>println method</p> Signup and view all the answers

    What will happen if you use a variable without ever assigning a value to it?

    <p>An error will occur.</p> Signup and view all the answers

    How should longer comments be formatted in code?

    <p>By enclosing them between specific delimiters.</p> Signup and view all the answers

    What is the effect of assigning a new value to a variable that already holds a value?

    <p>The new value simply replaces the old value.</p> Signup and view all the answers

    What is the proper way to comment a single line of code in this context?

    <p>// This is a comment</p> Signup and view all the answers

    What will the following statement do: width = 20;?

    <p>Update the current value of width to 20.</p> Signup and view all the answers

    What must be done before you can use a variable in your code?

    <p>It must be assigned a value.</p> Signup and view all the answers

    What do the accessor methods in the Rectangle class mainly provide?

    <p>Information about the rectangle's dimensions and position</p> Signup and view all the answers

    What is the purpose of the translate method in the Rectangle class?

    <p>To move the rectangle to a new position</p> Signup and view all the answers

    After executing box.translate(15, 25) on a rectangle initially at (5, 10), what will be the new coordinates of the top-left corner?

    <p>(20, 35)</p> Signup and view all the answers

    What characteristic of the translate method makes it a mutator?

    <p>It alters the rectangle's position in the plane.</p> Signup and view all the answers

    Which of the following methods is NOT an accessor method for the Rectangle class?

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

    What is represented by the term 'translation' in the context of geometry as applied to rectangles?

    <p>Moving the shape while keeping its dimensions constant</p> Signup and view all the answers

    What is included in the summary tables of the API documentation for each class?

    <p>Constructors and methods</p> Signup and view all the answers

    In the API documentation, what does the term 'application programming interface' refer to?

    <p>The methods and classes available for programming</p> Signup and view all the answers

    Which of the following statements about the width and height of a rectangle is correct after a translation operation?

    <p>They remain unchanged.</p> Signup and view all the answers

    What does the detailed description of a method include?

    <p>The actions the method performs</p> Signup and view all the answers

    What information is provided about parameter variables in the method description?

    <p>The types and names of the parameter variables</p> Signup and view all the answers

    What is a significant benefit of the standard library for programmers?

    <p>It contains a wide variety of methods for common tasks</p> Signup and view all the answers

    What should you expect to find when clicking on a method's link in the API documentation?

    <p>A detailed description of its functionality</p> Signup and view all the answers

    What type of value does a method return if it does not return any value?

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

    Which of the following is a common reason why beginners may find the API documentation intimidating?

    <p>The sheer number of available methods</p> Signup and view all the answers

    When would a programmer use the methods provided by the Rectangle class?

    <p>For computations involving rectangles</p> Signup and view all the answers

    What is the primary goal of the chapter on using objects?

    <p>To learn about variables and methods</p> Signup and view all the answers

    Which concept distinguishes objects from object references?

    <p>Objects represent actual data while object references point to memory locations</p> Signup and view all the answers

    Which statement best describes accessor and mutator methods?

    <p>Accessor methods retrieve attribute values, and mutator methods modify them.</p> Signup and view all the answers

    What is a likely purpose of browsing the API documentation?

    <p>To find and understand how to use libraries and classes</p> Signup and view all the answers

    Which of the following is NOT a part of the chapter's contents?

    <p>Creating digital art applications</p> Signup and view all the answers

    Why is it important to choose descriptive variable names?

    <p>To improve code readability and maintainability</p> Signup and view all the answers

    What is a common issue with undeclared or uninitialized variables?

    <p>They can lead to runtime errors or unexpected results.</p> Signup and view all the answers

    What does constructing an object involve?

    <p>Allocating memory for the object and initializing its attributes</p> Signup and view all the answers

    What is the benefit of implementing test programs?

    <p>To ensure that the code behaves as expected</p> Signup and view all the answers

    What would be an example of an argument in a method call?

    <p>A value passed to a method when it is called</p> Signup and view all the answers

    What is the primary purpose of environments like BlueJ and Dr.Java?

    <p>To assist in the interactive exploration of object behavior</p> Signup and view all the answers

    How does an object variable function in Java?

    <p>It contains a reference to the object's memory location</p> Signup and view all the answers

    What can users do in the BlueJ environment?

    <p>Construct and manipulate objects without coding</p> Signup and view all the answers

    Which class is explored to compute the number of days since birth in the provided example?

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

    Where can users obtain BlueJ?

    <p>Users can download it for free</p> Signup and view all the answers

    What is demonstrated through the use of the Picture class in the worked example?

    <p>Editing photos using class APIs</p> Signup and view all the answers

    What aspect of programming do environments like BlueJ promote?

    <p>Object-oriented thinking</p> Signup and view all the answers

    Which statement is true regarding object storage in Java?

    <p>The memory location of objects is tracked by object variables</p> Signup and view all the answers

    Study Notes

    Chapter 2: Using Objects

    • Chapter focuses on manipulating complex data, like bank accounts, employee records, or shapes, through objects
    • Java is ideal for creating and manipulating these objects
    • The chapter introduces variables, types, and assignments necessary for managing objects
    • Objects have methods that define their behavior
    • Method calls can provide data or modify object behavior
    • Accessor methods do not change object data, while mutator methods change data
    • Methods can have arguments (inputs) and return values (outputs)
    • Object variables do not contain the object itself, rather they hold the object's memory location

    Variables

    • Variables are storage locations in a program, with a name
    • Variables store values
    • Variables have a type that defines the kind of value they can hold
    • Integer type (int) stores whole numbers
    • Floating-point type (double) stores numbers with decimal parts
    • String type (String) stores text
    • Variables should be named descriptively, e.g. milesPerGallon rather than mpg
    • Variable names start with a lower case letter and can contain numbers or underscores. Names are case sensitive. Avoid reserved words, like double, class

    Comments

    • Comments explain code for human readers
    • Single-line comments use //
    • Multi-line comments use /* ... */
    • Comments are ignored by the compiler

    Assignment Operator

    • The = operator assigns a value to a variable
    • Variables must be initialized before use
    • Assignment can involve expressions, like width = height + 10

    Object Construction

    • Objects are built by invoking a constructor: new className (arguments)
    • When constructing objects, you need to supply the arguments that specify the initial properties of the object
    • Avoid invoking constructors as methods, instead create a new object using new

    Method Arguments

    • Arguments provide information to methods to determine what they do
    • Arguments are values supplied during a method call

    Return Values

    • Some methods compute and return a value
    • Return values are results of methods, which the method provides to the code that executed the method
    • void indicates a method that doesn’t return a value

    The API Documentation

    • The API (Application Programming Interface) documents Java libraries, including classes and methods, for programmers to reference
    • API documentation describes methods and classes, so programmers can figure out how to use them

    Packages

    • Java code is organized in packages (e.g., java.awt)
    • Use import statements to access classes from other packages: import java.awt.Rectangle;

    Testing

    • Test programs check that methods work correctly
    • Methods' expected results should be identified before running the test program

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    Related Documents

    Using Objects Chapter 2 PDF

    Description

    Test your knowledge on string methods, particularly the length method, and their functionality in programming. Learn about method return values, their applications, and the importance of comments in code. This quiz is essential for anyone looking to deepen their understanding of string manipulation in programming.

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