It's a pretty easy exercise, just need some help since I skipped class and left this till last minute.
It's writing unit tests for any implementations of an abstract class and interface.
Thanks
Not much of a java guy to be honest, but does something like this work?
I made this abstract class:
PHP Code
<?php
public abstract class Maths {
abstract double sqrt(double value, int sigfigs);
abstract double abs(double value);
}
And this interface:
PHP Code
<?php
public interface Rounder {
double round(double value, int places);
}
And this class called "Stuff" to use both of them.
PHP Code
<?php
public class Stuff extends Maths implements Rounder {
public double round(double value, int places) {
// truncates a java double into `places` places after the decimal
long pow = (long)Math.pow(10, places);
return (long)Math.round(value * pow) / (double)pow;
}
@Override
double abs(double value) {
// return the absolute value of a number
return (value >= 0 ? value : -value);
}
@Override
double sqrt(final double value, final int sigfigs) {
// a simple implementation of the babylonian method of determining the square root of a number
double prev = -1, curr = sigfigs * 100;
while(round(prev, sigfigs) != round(curr, sigfigs)) {
prev = curr;
curr = (prev + (value / prev)) / 2;
}
return round(curr, sigfigs);
}
}
And here's an example unit test you can write:
PHP Code
<?php
import org.junit.Test;
import org.junit.Assert;
public class Tester {
@Test
public void checkRounderRound(){
final double
input1 = 123.456, target1 = 123.46, epsilon1 = 0.0,
input2 = 999999.999999, target2 = 1000000.0, epsilon2 = 0.0,
input3 = 73737.3737, target3 = 73737.37, epsilon3 = 0.0;
final int
sigfigs1 = 2,
sigfigs2 = 5,
sigfigs3 = 2;
Rounder rounder = new Stuff(); // works fine because it implements rounder
Assert.assertEquals(rounder.round(input1, sigfigs1), target1, epsilon1);
Assert.assertEquals(rounder.round(input2, sigfigs2), target2, epsilon2);
Assert.assertEquals(rounder.round(input3, sigfigs3), target3, epsilon3);
}
@Test
public void checkMathsSqrt(){
final double
input1 = 100.0, target1 = 10.0, epsilon1 = 0.0,
input2 = 125348, target2 = 354.04519485512014, epsilon2 = 0.0,
input3 = 1, target3 = 1, epsilon3 = 0.0;
final int
sigfigs1 = 5,
sigfigs2 = 15,
sigfigs3 = 5;
Maths maths = new Stuff(); // works fine because it extends Maths
Assert.assertEquals(maths.sqrt(input1, sigfigs1), target1, epsilon1);
Assert.assertEquals(maths.sqrt(input2, sigfigs2), target2, epsilon2);
Assert.assertEquals(maths.sqrt(input3, sigfigs3), target3, epsilon3);
}
@Test
public void checkMathsAbs(){
final double
input1 = 100, target1 = 100, epsilon1 = 0.0,
input2 = -12345, target2 = 12345, epsilon2 = 0.0,
input3 = 0, target3 = 0, epsilon3 = 0.0;
Maths maths = new Stuff(); // works fine because it extends Maths
Assert.assertEquals(maths.abs(input1), target1, epsilon1);
Assert.assertEquals(maths.abs(input2), target2, epsilon2);
Assert.assertEquals(maths.abs(input3), target3, epsilon3);
}
}
(Nov 27, 2016 09:16 PM)Goodies Wrote: Not much of a java guy to be honest, but does something like this work?
I made this abstract class:
PHP Code
<?php
public abstract class Maths {
abstract double sqrt(double value, int sigfigs);
abstract double abs(double value);
}
And this interface:
PHP Code
<?php
public interface Rounder {
double round(double value, int places);
}
And this class called "Stuff" to use both of them.
PHP Code
<?php
public class Stuff extends Maths implements Rounder {
public double round(double value, int places) {
// truncates a java double into `places` places after the decimal
long pow = (long)Math.pow(10, places);
return (long)Math.round(value * pow) / (double)pow;
}
@Override
double abs(double value) {
// return the absolute value of a number
return (value >= 0 ? value : -value);
}
@Override
double sqrt(final double value, final int sigfigs) {
// a simple implementation of the babylonian method of determining the square root of a number
double prev = -1, curr = sigfigs * 100;
while(round(prev, sigfigs) != round(curr, sigfigs)) {
prev = curr;
curr = (prev + (value / prev)) / 2;
}
return round(curr, sigfigs);
}
}
And here's an example unit test you can write:
PHP Code
<?php
import org.junit.Test;
import org.junit.Assert;
public class Tester {
@Test
public void checkRounderRound(){
final double
input1 = 123.456, target1 = 123.46, epsilon1 = 0.0,
input2 = 999999.999999, target2 = 1000000.0, epsilon2 = 0.0,
input3 = 73737.3737, target3 = 73737.37, epsilon3 = 0.0;
final int
sigfigs1 = 2,
sigfigs2 = 5,
sigfigs3 = 2;
Rounder rounder = new Stuff(); // works fine because it implements rounder
Assert.assertEquals(rounder.round(input1, sigfigs1), target1, epsilon1);
Assert.assertEquals(rounder.round(input2, sigfigs2), target2, epsilon2);
Assert.assertEquals(rounder.round(input3, sigfigs3), target3, epsilon3);
}
@Test
public void checkMathsSqrt(){
final double
input1 = 100.0, target1 = 10.0, epsilon1 = 0.0,
input2 = 125348, target2 = 354.04519485512014, epsilon2 = 0.0,
input3 = 1, target3 = 1, epsilon3 = 0.0;
final int
sigfigs1 = 5,
sigfigs2 = 15,
sigfigs3 = 5;
Maths maths = new Stuff(); // works fine because it extends Maths
Assert.assertEquals(maths.sqrt(input1, sigfigs1), target1, epsilon1);
Assert.assertEquals(maths.sqrt(input2, sigfigs2), target2, epsilon2);
Assert.assertEquals(maths.sqrt(input3, sigfigs3), target3, epsilon3);
}
@Test
public void checkMathsAbs(){
final double
input1 = 100, target1 = 100, epsilon1 = 0.0,
input2 = -12345, target2 = 12345, epsilon2 = 0.0,
input3 = 0, target3 = 0, epsilon3 = 0.0;
Maths maths = new Stuff(); // works fine because it extends Maths
Assert.assertEquals(maths.abs(input1), target1, epsilon1);
Assert.assertEquals(maths.abs(input2), target2, epsilon2);
Assert.assertEquals(maths.abs(input3), target3, epsilon3);
}
}
Omg thanks this was a good enough example to give me an understanding <3
I'm done thanks to you :)
|
