Welcome to Lab 2
By the end of this Lab you should be able to do the following.
- create a simple equation using a constant
- Remember your simple Linux commands
Lab Topics
Here is an example program that exercises most of the routines in java.lang.Math. In particular notice there are constants defined for PI and E.
public class MathLibraryExample {
public static void main(String[] args) {
int i = 7;
int j = -9;
double x = 72.3;
double y = 0.34;
System.out.println("i is " + i);
System.out.println("j is " + j);
System.out.println("x is " + x);
System.out.println("y is " + y);
// The absolute value of a number is equal to
// the number if the number is positive or
// zero and equal to the negative of the number
// if the number is negative.
System.out.println("|" + i + "| is " + Math.abs(i));
System.out.println("|" + j + "| is " + Math.abs(j));
System.out.println("|" + x + "| is " + Math.abs(x));
System.out.println("|" + y + "| is " + Math.abs(y));
// Truncating and Rounding functions
// You can round off a floating point number
// to the nearest integer with round()
System.out.println(x + " is approximately " + Math.round(x));
System.out.println(y + " is approximately " + Math.round(y));
// The "ceiling" of a number is the
// smallest integer greater than or equal to
// the number. Every integer is its own
// ceiling.
System.out.println("The ceiling of " + i + " is " + Math.ceil(i));
System.out.println("The ceiling of " + j + " is " + Math.ceil(j));
System.out.println("The ceiling of " + x + " is " + Math.ceil(x));
System.out.println("The ceiling of " + y + " is " + Math.ceil(y));
// The "floor" of a number is the largest
// integer less than or equal to the number.
// Every integer is its own floor.
System.out.println("The floor of " + i + " is " + Math.floor(i));
System.out.println("The floor of " + j + " is " + Math.floor(j));
System.out.println("The floor of " + x + " is " + Math.floor(x));
System.out.println("The floor of " + y + " is " + Math.floor(y));
// Comparison operators
// min() returns the smaller of the two arguments you pass it
System.out.println("min(" + i + "," + j + ") is " + Math.min(i,j));
System.out.println("min(" + x + "," + y + ") is " + Math.min(x,y));
System.out.println("min(" + i + "," + x + ") is " + Math.min(i,x));
System.out.println("min(" + y + "," + j + ") is " + Math.min(y,j));
// There's a corresponding max() method
// that returns the larger of two numbers
System.out.println("max(" + i + "," + j + ") is " + Math.max(i,j));
System.out.println("max(" + x + "," + y + ") is " + Math.max(x,y));
System.out.println("max(" + i + "," + x + ") is " + Math.max(i,x));
System.out.println("max(" + y + "," + j + ") is " + Math.max(y,j));
// The Math library defines a couple
// of useful constants:
System.out.println("Pi is " + Math.PI);
System.out.println("e is " + Math.E);
// Trigonometric methods
// All arguments are given in radians
// Convert a 45 degree angle to radians
double angle = 45.0 * 2.0 * Math.PI/360.0;
System.out.println("cos(" + angle + ") is " + Math.cos(angle));
System.out.println("sin(" + angle + ") is " + Math.sin(angle));
// Inverse Trigonometric methods
// All values are returned as radians
double value = 0.707;
System.out.println("acos(" + value + ") is " + Math.acos(value));
System.out.println("asin(" + value + ") is " + Math.asin(value));
System.out.println("atan(" + value + ") is " + Math.atan(value));
// Exponential and Logarithmic Methods
// exp(a) returns e (2.71828...) raised
// to the power of a.
System.out.println("exp(1.0) is " + Math.exp(1.0));
System.out.println("exp(10.0) is " + Math.exp(10.0));
System.out.println("exp(0.0) is " + Math.exp(0.0));
// log(a) returns the natural
// logarithm (base e) of a.
System.out.println("log(1.0) is " + Math.log(1.0));
System.out.println("log(10.0) is " + Math.log(10.0));
System.out.println("log(Math.E) is " + Math.log(Math.E));
// pow(x, y) returns the x raised
// to the yth power.
System.out.println("pow(2.0, 2.0) is " + Math.pow(2.0,2.0));
System.out.println("pow(10.0, 3.5) is " + Math.pow(10.0,3.5));
System.out.println("pow(8, -1) is " + Math.pow(8,-1));
// sqrt(x) returns the square root of x.
for (i=0; i < 10; i++) {
System.out.println(
"The square root of " + i + " is " + Math.sqrt(i));
}
// Finally there's one Random method
// that returns a pseudo-random number
// between 0.0 and 1.0;
System.out.println("Here's one random number: " + Math.random());
System.out.println("Here's another random number: " + Math.random());
}
}
Programming Problem
Create a program that asks the user for the radius of a circle and then calculates and prints out the the diameter, the circumference, and the area of a circle with that radius.
