22 Questions
What is the purpose of System.out.println in Java?
To print output to the console and move to a new line
How is the data to be output given in System.out.println?
Through a plus sign
What is the difference between System.out.println and System.out.print?
println generates a new line, print does not
What is the purpose of importing packages and classes in Java?
To make libraries easily accessible to programs
Which package is automatically imported into every Java program?
java.lang.Integer
What is the benefit of specifying a class instead of using (*) when importing packages?
It avoids naming conflicts
Which class in Java is used for simple keyboard input starting from version 5.0?
Scanner
What statement is required to make the Scanner class available to a Java program?
import java.util.Scanner;
What object is created by the following code: Scanner keyboard = new Scanner(System.in);?
keyboard
Which method reads one int value typed at the keyboard and assigns it to a variable?
nextInt()
What does the method 'nextDouble' do in Java's Scanner class?
Reads a double value
How are multiple inputs separated when using the Scanner class?
By whitespace
When using 'keyboard.next()', how is a string read?
Reads one string of non-whitespace characters delimited by whitespace
'keyboard.nextLine()' reads what in Java?
'\n' character input when the Enter key pressed
What can happen when combining 'nextInt()' method and 'nextLine()' method in Java?
There might be problems due to line terminator characters
What does whitespace refer to in Java's Scanner class context?
Blank spaces, tabs, and line breaks that separate inputs
What is the value of the variable n
in the given code?
2
What is the value of the variable s1
in the given code?
""
What is the value of the variable s2
in the given code?
"heads are better than"
When should a program prompt the user for input?
Whenever the program needs data from the user
What is the purpose of echoing the user's input in a program?
To expose subtle errors in the user's input
How can the input delimiter be changed when using the Scanner
class?
By calling the useDelimiter()
method
Study Notes
Output in Java
-
System.out
is an object that is part of the Java language. -
println
is a method invoked by theSystem.out
object, used for console output. - The data to be output is given as an argument in parentheses.
- A plus sign is used to connect more than one item.
- Every invocation of
println
generates a new line after it finishes.
Differences between println
and print
-
print
is a method that can be invoked by theSystem.out
object. -
print
is similar toprintln
, except that it does not generate a new line. - With
println
, the next output goes on a new line. - With
print
, the next output goes on the same line.
Importing Packages and Classes
- Libraries in Java are called packages.
- A package is a collection of classes that is stored in a manner that makes it easily accessible to any program.
- To use a class that belongs to a package, the class must be imported using an
import
statement. - Classes found in the package
java.lang
are imported automatically into every Java program. - It is better to specify the class instead of using the
*
wildcard.
Console Input Using the Scanner Class
- The
Scanner
class is used for simple keyboard input. - The
Scanner
class is included in Java starting from version 5.0. - To use the
Scanner
class, a program must include theimport java.util.Scanner
statement. - The
Scanner
class is used to create an object that reads input from the keyboard. - The
Scanner
object can be given any name.
Methods in the Scanner Class
-
nextInt()
reads oneint
value typed in at the keyboard and assigns it to a variable. -
nextDouble()
reads onedouble
value typed in at the keyboard and assigns it to a variable. -
next()
reads one string of non-whitespace characters delimited by whitespace characters. -
nextLine()
reads an entire line of keyboard input. - Multiple inputs must be separated by whitespace and read by multiple invocations of the appropriate method.
Pitfalls of Using the Scanner Class
- The
nextLine()
method reads the remainder of a line of text starting wherever the last keyboard reading left off. - This can cause problems when combining it with different methods for reading from the keyboard.
Programming Tips
- A program should always prompt the user when they need to input some data.
- A program should always echo all input that it receives from the keyboard.
Other Input Delimiters
- The delimiters that separate keyboard input can be changed when using the
Scanner
class. - The
useDelimiter()
method can be used to change the input delimiter.
Test your knowledge on how to use the System.out.println method in Java for console output. Learn about providing arguments, connecting multiple items, and generating new lines. Also, compare println with the print method.
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