Download Simple Console Output

Simple Console Output
CS 21a
What we will briefly discuss
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System.out.println( … )
System.out.print( … )
System.out.printf( … )
Consider the following program
File: RevisedHello.java
// Revised Hello World application
public class RevisedHello
{
public static void main( String args[] )
{
System.out.println( “Hello world” );
System.out.println( “Good morning” );
System.out.println( “Java is cool” );
}
}
System.out.println()
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println() will display each string on a
separate line
Hello world
Good Morning
Java is cool
How about using print()?
File: RevisedHello.java
// Revised Hello World application
public class RevisedHello
{
public static void main( String args[] )
{
System.out.print( “Hello world” );
System.out.print( “Good morning” );
System.out.print( “Java is cool” );
}
}
System.out.print()
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print() will NOT print the next string on
a new line
Hello worldGood MorningJava is cool
System.out.print()
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Another example
System.out.println( “Hello world” );
System.out.print( “Good morning” );
System.out.println( “Java is cool”);
System.out.println( “So is our teacher” );
Hello world
Good MorningJava is cool
So is our teacher
Try this…
File: RevisedHello.java
// Revised Hello World application
public class RevisedHello
{
public static void main( String args[] )
{
System.out.print( “Hello world” + “\n” );
System.out.print( “Good morning” + “\n” );
System.out.print( “Java is cool” + “\n” );
}
}
Using print() with “\n”
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Even if print() does not display
consecutive strings in separate lines,
the “\n” character causes a line break
The same effect of println() can be
achieved
Now try this…
File: AdvancedExample.java
// A demonstration of printf()
public class AdvancedExample
{
public static void main( String args[] )
{
double pi = Math.PI;
System.out.println( pi );
}
}
//note: pi is a variable assigned to the value of pi.
//Math.PI is a constant value from Math.java
//More on this in our future lessons
Formatting numbers
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The code will display
3.141592653589793 on the console
What if we want to force pi to be
displayed with up to just 3 decimal
places?
System.out.printf()
File: AdvancedExample.java
// A demonstration of printf()
public class AdvancedExample
{
public static void main( String args[] )
{
double pi = Math.PI;
System.out.printf("pi = %5.3f \n", pi);
}
}
System.out.printf()
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The line
System.out.printf("pi = %5.3f \n", pi);
will cause pi to be displayed as 3.142
Format Specifiers
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Indicates how the arguments
should be processed and
where they should be
inserted
Syntax
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% - start of the specifier
width (optional)
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'.' + precision (optional)
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minimum number of
spaces to print argument
puts blanks in unused
spaces
number of digits after
decimal
Conversion character
Conversion
Formatted into:
d
integers
f
floating-point number
s
String
c
character
Summary of printf example
System.out.printf("pi = %5.3f \n", pi);
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The % symbol signifies the start of the
specifier
5 means that the width value of the number
is 5 characters
The precision value 3 means that 3 decimal
places are required
The conversion character f means that the
resulting pi is a floating-point number
\n results in a line break