CS 115

OBJECT ORIENTED PROGRAMMING ILECTURE 4 part 3

GEORGE KOUTSOGIANNAKIS

Topic

• Math Library Class.

About the Math Library class

• The Math class provides static constants and static methods for performing common calculations.

• The Math class is in the java.lang package, so it does not need to be imported

• The methods of this class are all static.– A static method is a method that can be invoked (called)

by using the name of the class that it belongs and the . Operator

– For example to call the method random ( a method that produces random numbers) we use

Math.random();

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Math Library class

• Checking the API documentation for random we see the description:

public static double random() Returns a double value with a positive sign, greater than or equal to 0.0 and less than 1.0. Returned values are chosen pseudorandomly with (approximately) uniform distribution from that range.

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Math Library class

Two static constants PI - the value of pi E - the base of the natural logarithm Example: System.out.println( Math.PI ); System.out.println( Math.E );

The output is: 3.141592653589793 2.718281828459045

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Sample Methods of the Math ClassReturn type Method name and argument list

dataTypeOfArg abs( dataType arg )

returns the absolute value of the argument arg, which can be a double, float, int or long.

double log( double a )

returns the natural logarithm (in base e) of its argument.

double sqrt( double a )

returns the positive square root of a

double

pow( double base, double exp )

returns the value of base raised to the power exp

The Math min/max Methods

Find smallest of three numbers: int smaller = Math.min( num1, num2 ); int smallest = Math.min( smaller, num3 );

See Example 3.16 in Text -MathMinMaxMethods.java

Return type Method name and argument listdataTypeOfArgs min( dataType a, dataType b )

returns the smaller of the two arguments. The arguments can be doubles, floats, ints, or longs.

dataTypeOfArgs max( dataType a, dataType b )

returns the larger of the two arguments. The arguments can be doubles, floats, ints, or longs.

Another Example program using the Math Class

import java.util.Scanner;public class MyMathClass{

public static void main(String[] args) {

double exponent=4.0;double result=0.00;double sqrt=0.00;

result=Math.pow(10, exponent);

sqrt=Math.sqrt(exponent);System.out.println("The result is"+“ "+result);System.out.println("The square root of the number”+” “++exponent+” ”+” is"+” “+sqrt);

}}

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