A simple Math.pow example, display 2 to the power of 8.
In Math
2^8 = 2x2x2x2x2x2x2x2 =256
In Java
Math.pow(2, 8)
TestPower.java
package com.mkyong.test;
import java.text.DecimalFormat;
public class TestPower {
static DecimalFormat df = new DecimalFormat(".00");
public static void main(String[] args) {
//1. Math.pow returns double, need cast, display 256
int result = (int) Math.pow(2, 8);
System.out.println("Math.pow(2, 8) : " + result);
//2. Wrong, ^ is a binary XOR operator, display 10
int result2 = 2 ^ 8;
System.out.println("2 ^ 8 : " + result2);
//3. Test double , display 127628.16
double result3 = Math.pow(10.5, 5);
System.out.println("Math.pow(10.5, 5) : " + df.format(result3));
}
}
Output
Math.pow(2, 8) : 256
2 ^ 8 : 10
Math.pow(10.5, 5) : 127628.16
package lib;
public class MyNumFormat
{
public static double pow(double base, int exponent)
{
double base1 = 1;
for(int i = 0; i < exponent; i++)
{
base1 *= base;
}
return base1;
}
/**
* round – takes in a real # and rounds it up or down to a whole number.
*
* @param val
* – the value to round up or down.
* @return a whole number representing the rounded value.
*/
public static int round(double num)
{
return (int)(num + 0.5);
}
/**
* roundXDigits – rounds a number a certain number of places after the
* decimal.
*
* @param val
* – the value to round
* @param place
* – the # of places after the decimal that gets rounded up or
* down
* @return the real # rounded up/down in the correct place.
*/
public static double roundXDigits(double num, int place)
{
double tenPow = pow(10, place);
return round(num * tenPow) / tenPow;
}
/**
* dollarsToMoney – represents a real# as a money string
*
* @param val
* – the real# representing dollars and cents
* @return a String in the format of $#.##
*/
public static String dollarsToMoney(double val)
{
String start = "$";
start += val;
return start;
}
/**
* centsToMoney – uses the dollarsToMoney function to change 153 cents to
* $1.53
*
* @param val
* – the number of pennies given
* @return the money String represented as $#.## as outlined in the
* dollarsToMoney function.
*/
public static String centsToMoney(double val)
package lib;
public class MyNumFormat
{
public static double pow(double base, int exponent)
{
double base1 = 1;
for(int i = 0; i < exponent; i++)
{
base1 *= base;
}
return base1;
}
/**
* round – takes in a real # and rounds it up or down to a whole number.
*
* @param val
* – the value to round up or down.
* @return a whole number representing the rounded value.
*/
public static int round(double num)
{
return (int)(num + 0.5);
}
/**
* roundXDigits – rounds a number a certain number of places after the
* decimal.
*
* @param val
* – the value to round
* @param place
* – the # of places after the decimal that gets rounded up or
* down
* @return the real # rounded up/down in the correct place.
*/
public static double roundXDigits(double num, int place)
{
double tenPow = pow(10, place);
return round(num * tenPow) / tenPow;
}
/**
* dollarsToMoney – represents a real# as a money string
*
* @param val
* – the real# representing dollars and cents
* @return a String in the format of $#.##
*/
public static String dollarsToMoney(double val)
{
String start = "$";
start += val;
return start;
}
/**
* centsToMoney – uses the dollarsToMoney function to change 153 cents to
* $1.53
*
* @param val
* – the number of pennies given
* @return the money String represented as $#.## as outlined in the
* dollarsToMoney function.
*/
public static String centsToMoney(double val)
{
val /= 100;
return dollarsToMoney(val);
}
}
thanks
How could we use exponential in java, to evaluate expression with floating values.