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 billionto+2 billion  double4.9x to1.8x  float1.4x to3.4x10 38

Converting doubles to ints  When we convert, we will typically lose something.  Consider converting 12.9 to an int. There is no int  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 int i; 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:  double4.9x10-324to1.8x  float1.4x10-45to3.4x10+38  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?

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

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

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++;

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--;

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;

Convert the following to Java expressions:

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 Calculates the circumference. 3. Calculates the area. 4. 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 Calculates the circumference. 3. Calculates the area. 4. 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 //Calculate the circumference. //Calculate the area. //Print out the radius, circumference, and area. } //end main } //end class

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?

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

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

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

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

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

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

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

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