Int x 10 int y x 2 systemoutprint x x y y x11 y22

int x = 10;
int y =
x++
* 2;
System.out.print( " x= " +x + " y= " + y);
x=11 y=22
output
x=11 y=20
output
27
Quiz on pre/post increment/decrement
What is the output of the program below?
public class Ops
{ public static void main(String[] args)
{
int a = 10,p,q,r,s;
p = a++; // assign a to p then add 1
q = ++a; // add one to a then assign to q
r = --a;
s = a--;
System.out.println("p = " + p);
System.out.println("q = " + q);
System.out.println("r = " + r);
System.out.println("s = " + s);
System.out.println("a = " + a);
}
}
Ans: _______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
28

Operator precedence & Associative Rule
Category Operators Associativity
Operations on references
. []
L to R
Unary
++ -- ! - (type)
R to L
Multiplicative
* / %
L to R
Additive
+ -
L to R
Shift (bitwise)
<< >> >>>
L to R
Relational
< <= > >= instanceof
L to R
Equality
== !=
L to R
Boolean (or bitwise) AND
&
L to R
Boolean (or bitwise) XOR
^
L to R
Boolean (or bitwise) OR
|
L to R
Logical AND
&&
L to R
Logical OR
||
L to R
Conditional
?:
R to L
Assignment
= *= /= %= += -=
R to L
• Order in which operations are evaluated are based on precedence chart
(below) and associative rule.
• Associative Rule: Operators with equal precedence are carried out from left
to right, except for = operator (which is right to left)
•
29
Order of Evaluation:
Expression 3 + 8 * 4 > 5 * ( 4 + 3 ) - 1
3 + 8 * 4 > 5 * (4 + 3) - 1
3 + 8 * 4 > 5 * 7 – 1
3 + 32 > 5 * 7 – 1
3 + 32 > 35 – 1
35 > 35 – 1
35 > 34
true
(1) Inside parentheses first
(2) Leftmost * next (* / % group)
(3) Remaining * next (* / % group)
(4) Leftmost + next (+- group)
(5) Remaining – next (+- group)
(6) > next
30
IF IN DOUBT YOU CAN ALWAYS USE EXTRA PARENTHESES!

3 Predefined Objects for Input/Output
System.out
PrintStream
System.err
PrintStream
Input a line
Error in Input
System.out.println("Input a line");
System.err.println("Error in Input");
System.in
InputStream
String message = System.in.nextLine(); ?
No Such method !
31
Output using print()
import java.util.Scanner;
public class SumDemo2 {
public static void main (String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter value for n1 : ");
double n1 = keyboard.nextDouble();
System.out.print("Enter value for n2 : ");
double n2 = keyboard.nextDouble();
double sum = n1 + n2;
System.out.print("Sum of "+n1+ " and " + n2 +
" is " + sum);
}
}
Unlike print(), printf() allows setting width & decimal places directly.
32

Formatted output using printf()
import java.util.Scanner;
public class SumDemo3 {
public static void main (String[] args)
{
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter value for n1 : ");
double n1 = keyboard.nextDouble();
System.out.print("Enter value for n2 : ");
double n2 = keyboard.nextDouble();
double sum = n1 + n2;
System.out.printf("Sum of %.2f and %.2f is %.2f",
n1, n2, sum);
}
}
2
2 2
33
Commonly used printf()/String.format
conversion symbols
General Syntax
%[argument_index$][flags][width][.precision]conversion
Sample conversions
•%c
a character
•%d
a decimal integer
•%f
a floating point number
•%s
a string
•%b
a boolean value
See
* See also
java.lang.String.format()
method
34

Using width and precision modifiers in
printf()
In the previous program changing last statement to
System.out.printf("Sum of %10.2f and %8.2f is %6.2f",
n1, n2, sum);
produces the following results:
10
8
6
35
Tabulating output using printf()