Questions and Answers
What are variables of the boolean data type useful for?
Evaluating conditions that are either true or false.
In the following Java statement, what value is stored in the variable name? String name = "John Doe";
The memory address where 'John Doe' is located.
Named constants are initialized with a value, and that value cannot change during the execution of the program.
True
Both character literals and string literals can be assigned to a char variable.
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What would be displayed as a result of the following code? int x = 578; System.out.print("There are " + x + 5 + "/n" + "hens in the hen house");
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Programming style includes techniques for consistently putting spaces and indentation in a program so visual cues are created.
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What will be the value of z after the following statements have been executed? int x = 4, y = 33; double z; z = (double) (y/x);
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A variable's scope is the part of the program that has access to the variable.
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The Java API provides a class named Math, which contains numerous methods that are useful for performing complex mathematical operations.
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What output will be displayed as a result of executing the following code? int x=5, y=20; x+=32; y/=4; System.out.println("x = " + x + ", y = " + y );
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Which Scanner class method reads a String?
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Which of the following statements is invalid? double r = 2.9X106;
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A message dialog is a quick and simple way to ask the user to enter data.
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The boolean data type may contain the following range of values:
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The primitive data types only allow a(n) ________ to hold a single value.
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Which of the following is not a rule that must be followed when naming identifiers?
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Unlike a console program, a program that uses JOptionPane does not automatically stop executing when the end of the main method is reached.
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What is the result of the following expression? 10+5*3-20
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Which of the following is not a valid Java comment?
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Which of the following statements will correctly convert the data type, if x is a float and y is a double?
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To print "Hello, world" on the monitor, use the following Java statement:
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A Java program must have at least one
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What is the result of the following expression? 17 % 3 * 2 - 12 + 15
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When you call one of the Scanner class's methods to read a primitive value, such as nextInt or nextDouble, and then call the nextLine method to read a string, an annoying and hard-to-find problem can occur.
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Character literals are enclosed in ________, and string literals are enclosed in ________.
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This is a named storage location in the computer's memory.
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The simplest way you can use the System.out.printf method is
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What will be displayed after the following statements have been executed? int x = 15, y = 20, z = 32; x+=12; y/=6; z-=14; System.out.println("x = " + x + ", y = " + y + ", z=" + z);
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When saving a Java source file, save it with an extension of
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What will be the value of z as a result of executing the following code? int x =5, y = 28; float z; z = (float) (y/x);
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If you use a flag in a format specifier, you must write the flag before the field width and the precision.
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What will be displayed when the following code is executed? final int x = 22, y = 4; y +=x; System.out.println("x = " + x + ", y = " + y);
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This statement tells the compiler where to find the JOptionPane class and makes it available to your program.
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The ________ method is used to display a message dialog.
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The System.out.printf method allows you to format output in a variety of ways.
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A(n) ________ is a dialog box that prompts the user for input.
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If you wish to use the System.out.printf method to print a string argument, use the ________ format specifier.
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This is a value that is written into the code of a program.
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Which of the following statements correctly creates a Scanner object for keyboard input?
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Variables are classified according to their
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Study Notes
Boolean Data Type
- Boolean variables evaluate conditions as either true or false.
- The boolean data type only supports two values: true or false.
String Variables in Java
- In Java, when defining a string variable like
String name = "John Doe";, the variablenameholds the memory address of the string rather than the string itself.
Constants and Variables
- Named constants are initialized once and cannot be modified during program execution.
- Primitive data types require a variable to store a single value.
Character and String Literals
- Character literals are enclosed in single quotes, while string literals use double quotes.
- Only string literals can be assigned to string variables, not character literals.
Output and Expression Evaluation
- Complex expressions and print statements may not behave as expected; for instance, string concatenation can lead to output like "There are 5785 hens in the hen house."
- Expressions are evaluated according to operator precedence; for example,
10 + 5 * 3 - 20results in 5.
Data Type Conversions
- Data types can be converted using casts; for example,
x = (float)y;converts a doubleyinto a floatx. - The Scanner class reads values using methods like
nextLinefor strings,nextIntfor integers, etc.
Programming Style
- Consistent formatting, including spaces and indentation, enhances readability and creates visual cues.
- The
System.out.printfmethod is versatile for formatting output, requiring only a format string to function.
Scope and Access
- A variable's scope defines where in the program it can be accessed and used.
- To create a program that prompts for user input, the JOptionPane class provides methods like
showMessageDialog.
Comments and Errors
- Java comments must follow specific syntax; invalid comments include
*/ Comment 2 /*. - Errors in code, such as modifying a final variable, prevent successful compilation.
Input Dialogs and Literals
- An input dialog prompts users for input and is implemented with specific methods from the JOptionPane class.
- Literals are fixed values written into the code, distinguishing them from variables.
Basic Constructs in Java
- A Java program must include at least one class definition.
- Understanding the Scanner class is crucial for managing user input from the keyboard.
Conclusion and Usage
- Use
System.out.printlnfor displaying text on the console, and ensure correct data type usage to prevent runtime errors. - Variables are classified by their data types, forming the backbone of programming logic and data management in Java.
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Description
Test your knowledge of key concepts from Programming Chapter 13 with these flashcards. Each card helps reinforce your understanding of boolean data types, variable assignments, and named constants in programming. Get ready to master these essential programming concepts!
