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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.

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Presentation Transcript
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:
• 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?

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.

//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.

//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.

//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.

//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.

//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.

//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.

//Calculate the circumference.

double circ = 2 * Math.PI * radius;

//Calculate the area.

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

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.

//Calculate the circumference.

double circ = 2 * Math.PI * radius;

//Calculate the area.