1. Today’s topic:
Arithmetic expressions

2. Arithmetic expressions
binary (two arguments) arithmetic operators
+, -, *, /, % (mod or modulus)
unary (one arg) operators
-, +
Order of operations just like you’d expect:
Please Excuse My Dear Aunt Sadie.
Can user () to override.

3. Arithmetic expressions
How would we code the following?
Let n be 2 and k be 2n+1.

4. Arithmetic expressions
How would we code the following?
Let n be 2 and k be 2n+1.
int n = 2;
int k = 2*n+1; Or
int n, k;
n = 2;
k = 2 * n + 1;

5. Arithmetic expressions
How would we code the following?
Let n be 2 and k be 2n+1.
int n = 2;
int k = 2*n+1;
Note: The rhs of the equals is always evaluated first and is assigned to the lhs. Therefore, you cannot say:
int 2 = n; Or
2*n+1 = k;

6. Arithmetic expressions
Example from physics: F = M A (force = mass x acceleration).
How would we code this in Java?

7. Arithmetic expressions
Example from physics: F = M A (force = mass x acceleration).
How would we code this in Java?
double mass = 12.0;
double acc = 13.9;
double force = mass * acceleration;
System.out.println( “force = “ + force );

8. Differences between int and double
int (integer) and double (real numbers) are different.
int is a subset of double but ints are much faster to calculate than doubles
So use ints whenever you can but be aware of the following:
int n = 5/2;
int k = 9/10;

9. Differences between int and double
5 is an int.
5.1 is a double.
5.0 is a double.
5.7f is a float
Range of values:
int -2 billion to +2 billion
double 4.9x to 1.8x10308
float 1.4x10-45 to 3.4x1038

10. Converting doubles to ints
When we convert, we will typically lose something.
Consider converting 12.9 to an int. There is no int 12.9.
So the compiler will issue a message. To inform the compiler that we really wish to do this, we can use a cast.
int i;
double d = 12.9;
i = (int) d; //What do you think is in i now?

11. Converting doubles to ints
int i;
double d = 12.9;
i = (int) d; //What do you think is in i now?
//how can we round instead?

12. ints and mod (%) What is the result of the following: int k = 5 / 2;
What is the remainder?
% is used to calculate the remainder.
int remainder = 5 % 2;

13. Float vs. double Recall range of values:
double 4.9x to 1.8x10308
float 1.4x10-45 to 3.4x1038
Recall that we used a cast to convert a double to an int:
double d = 12.9;
int i = (int) d;
This is because a double won’t fit into an int. Will a double fit into a float?

14. Increment and decrement operators (++ and --)
What does the following do:
int i = 12;
i = i + 2;

15. Increment and decrement operators (++ and --)
We often see code like the following:
int value = 12; …
value = value + 1;

16. Increment and decrement operators (++ and --)
We often see code like the following:
int value = 12; …
value = value + 1;
int value = 12; … value++; //post increment ++value; //pre increment value++;

17. Increment and decrement operators (++ and --)
We often see code like the following:
int value = 12; …
value = value - 1;
int value = 12; … value--; //post decrement --value; //pre decrement value--;

18. Increment and decrement operators (++ and --)
We can use these operators in expressions as well (but don’t get carried away):
int where = 92;
int k = 7;
where = k++;
int j = --where;

19. Convert the following to Java expressions:

20. Write a program that . . .
class MyProgramTemplate { public static void main ( String param[] ) { System.out.println( "hi there" ); } //end main } //end class

21. Write a program that . . .
Declares a variable for the radius of a circle with a value of 12.7.
Calculates the circumference.
Calculates the area.
Prints out the radius, circumference, and area.
class MyProgramTemplate {
public static void main ( String param[] ) {
System.out.println( "hi there" );
} //end main
} //end class

22. Write a program that . . .
Declares a variable for the radius of a circle with a value of 12.7.
Calculates the circumference.
Calculates the area.
Prints out the radius, circumference, and area.
class MyProgramTemplate {
public static void main ( String param[] ) {
System.out.println( "hi there" );
//Declare a variable for the radius of a circle with a value of 12.7.
//Calculate the circumference.
//Calculate the area.
//Print out the radius, circumference, and area.
} //end main
} //end class

23. Write a program that . . .
class MyProgramTemplate { public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of //Calculate the circumference. //Calculate the area. //Print out the radius, circumference, and area. } //end main } //end class
What types of things are radius, circumference, and area?

24. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. //Calculate the area. //Print out the radius, circumference, and area. } //end main

25. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = ?; //Calculate the area. //Print out the radius, circumference, and area. } //end main

26. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * 3.14 * radius; //Calculate the area. //Print out the radius, circumference, and area. } //end main

27. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. //Print out the radius, circumference, and area. } //end main

28. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. } //end main

29. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. System.out.println( " radius = " + radius ); ? } //end main

30. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. System.out.println( " radius = " + radius ); System.out.println( " circumference = " + circ ); System.out.println( " area = " + area ); System.out.println( " Bye."); } //end main

31. Write a program that . . .
public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. System.out.print( " radius = " + radius + ", " ); System.out.print( " circumference = " + circ + ", " ); System.out.println( " area = " + area + "." ); System.out.println( " Bye."); } //end main