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Today’s topic:

- Arithmetic expressions

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 use () to override.

Arithmetic expressions

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

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;

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;

Arithmetic expressions

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

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 );

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;

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 4.9x10-324 to 1.8x10308
- float 1.4x10-45 to 3.4x1038

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?

Converting doubles to ints

inti;

double d = 12.9;

i = (int) d; //What do you think is in i now?

//how can we round instead?

Let’s check what we’ve learned so far (using jGrasp).

class FirstExample {

public static void main ( String[] params ) {

//arithmetic

//output

}

}

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;

Float vs. double

- Recall range of values:
- double 4.9x10-324 to 1.8x10+308
- float 1.4x10-45 to 3.4x10+38
- Recall that we used a cast to convert a double to an int:
- double d = 12.9;
- inti = (int) d;
- This is because a double won’t fit into an int. Will a double fit into a float?

Increment and decrement operators (++ and --)

- What does the following do:
- inti = 12;
- i = i + 2;

Increment and decrement operators (++ and --)

- We often see code like the following:

int value = 12;

…

value = value + 1;

…

value = value + 1;

…

value = value + 1;

Increment and decrement operators (++ and --)

- We often see code like the following:

int value = 12;

…

value = value + 1;

…

value = value + 1;

…

value = value + 1;

int value = 12;

…

value++; //post increment

…

++value; //pre increment

…

value++;

Increment and decrement operators (++ and --)

- We often see code like the following:

int value = 12;

…

value = value - 1;

…

value = value - 1;

…

value = value - 1;

int value = 12;

…

value--; //post decrement

…

--value; //pre decrement

…

value--;

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;

Write a program that . . .

class MyProgramTemplate {

public static void main ( String param[] ) {

System.out.println( "hi there" );

} //end main

} //end class

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

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

Write a program that . . .

What types of things are 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

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 12.7.

double radius = 12.7;

//Calculate the circumference.

//Calculate the area.

//Print out the radius, circumference, and area.

} //end main

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 12.7.

double radius = 12.7;

//Calculate the circumference.

double circ = ?;

//Calculate the area.

//Print out the radius, circumference, and area.

} //end main

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 12.7.

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

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 12.7.

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

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 12.7.

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

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 12.7.

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

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 12.7.

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

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 12.7.

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

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