Department of Computer Science
Faculty of Physical Sciences
Ahmadu Bello University, Zaria

COSC 211 : Object Oriented Programming I - LAB01

Objectives

To gain experience with:

• Printing Programs Output
• Escape Sequences
• Assignment

Printing Output

A print statement is actually a call to the print or println method of the System.out object. The print method takes exactly one argument or no arguments. However, it can take string or numeric value

There are three kinds of print statements in java:

1. System.out.print(argument) just print out its argument.

   Example1: Type and run the following program and observe the output

   //Printing.java
   public class Printing{
   	public static void main(String[] args){
   		System.out.print("Computer");
   		System.out.print("Science");
   		System.out.print("Department");
   	}
   }
   		

2. System.out.println(argument) prints out its argumenta nd ends the line.

   Example2: Modify the example1 program above, save as PrintLine.java, and compile, run, and observe the output

   Note that "print" is to be replaced with "println" method

   //PrintingLine.java
   public class PrintingLine{
   	public static void main(String[] args){
   		System.out.println(Computer");
   		System.out.println("Science");
   		System.out.println("Department");
   	}
   }
   		

3. System.out.printf(format, argument), gives more control over how things are printed.

   Format String::

   Composed of literals and format specifiers. Arguments are required only if there are format specifiers in the format string. Format specifiers include: flags, width, precision, and conversion characters in the following sequence:

   % [flags] [width] [.precision] conversion-character ( square brackets denote optional parameters )

   Flags:

   - : left-justify ( default is to right-justify )
   + : output a plus ( + ) or minus ( - ) sign for a numerical value
   0 : forces numerical values to be zero-padded ( default is blank padding )
   , : comma grouping separator (for numbers > 1000)
     : space will display a minus sign if the number is negative or a space if it is positive
   		

   Width:

   Specifies the field width for outputting the argument and represents the minimum number of characters to be written to the output. Include space for expected commas and a decimal point in the determination of the width for numerical values.

   Precision:

   Used to restrict the output depending on the conversion. It specifies the number of digits of precision when outputting floating-point values or the length of a substring to extract from a String. Numbers are rounded to the specified precision

   Conversion-Characters:

   d : decimal integer [byte, short, int, long]
   f : floating-point number [float, double]
   c : character Capital C will uppercase the letter
   s : String Capital S will uppercase all the letters in the string
   h : hashcode A hashcode is like an address. This is useful for printing a reference
   n : newline Platform specific newline character- use %n instead of \n for greater compatibility
   

Example3: Study, type, run and compile the following program and observe the output

//PrintingFormat.java
public class PrintingFormat{
	public static void main(String[] args){
		System.out.printf("%d",60);
		System.out.println();
		
		System.out.printf("%03d%n",9);
		
		System.out.printf("PI %.3f",3.141527);
		System.out.println();
		
		System.out.printf("Total is: N%,.2f%n", 84785.8978);
		
		System.out.printf("%-10S%n","Department of Computer Science");
		
		System.out.printf("% .2f",-67.8917);
		System.out.println();
		
		System.out.printf("% .2f",67.8917);
		System.out.println();
		
		System.out.printf("%C",'a');
		System.out.println();

	}
}
		

Escape Sequence

A character preceded by a backslash (\) is an escape sequence and has a special meaning to the compiler.

Following table shows the Java escape sequences -

When an escape sequence is encountered in a print statement, the compiler interprets it accordingly.

Example: Study, Type, compile and run the following program and observe the output

// EscapeSequence.java
public class EscapeSequence {

 public static void main(String args[]) {
  System.out.println("ABU said \"To pass, you must work hard!\".\n");
  System.out.println("Two Sided Triangles\n*\t*****\n**\t ****\n***\t  ***\n****\t   **\n*****\t    *\n");
  System.out.println("A Diamond \n  *\n\r ***\n\r*****\n ***\n  *\n");
  System.out.println("A Letter S\n  *\n\b*   *\n  *  \n*   *\n  *");
  System.out.println(" E =   46.12 * 6.9 - 2.5 * 10\n\t\b______________________\n\t   90.5 * 11.6");
 }
}
		

Assignment

1. Write a program that displays the following pattern

2. Write a program that displays the following table

	1	2	3	4
1   	1	2	3	4
2	2	4	6	16
3	3	6	9	12
4	4	8	12	16