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Cars, Assemble!

Welcome to Cars, Assemble! on Exercism's Java Track. If you need help running the tests or submitting your code, check out HELP.md. If you get stuck on the exercise, check out HINTS.md, but try and solve it without using those first :)

Introduction

There are two different types of numbers in Java:

  • Integers: numbers with no digits behind the decimal separator (whole numbers). Examples are -6, 0, 1, 25, 976 and -500000.
  • Floating-point numbers: numbers with zero or more digits behind the decimal separator. Examples are -20.4, 0.1, 2.72, 16.984025 and 1024.0.

The two most common numeric types in Java are int and double. An int is a 32-bit integer and a double is a 64-bit floating-point number.

Arithmetic is done using the standard arithmetic operators. Numbers can be compared using the standard numeric comparison operators and the equality (==) and inequality (!=) operators.

Java has two types of numeric conversions:

  1. Implicit conversions: no data will be lost and no additional syntax is required.
  2. Explicit conversions: data could be lost and additional syntax in the form of a cast is required.

As an int has less precision than a double, converting from an int to a double is safe and is thus an implicit conversion. However, converting from a double to an int could mean losing data, so that requires an explicit conversion.

In this exercise you must conditionally execute logic. The most common way to do this in Java is by using an if/else statement:

int x = 6;

if (x == 5) {
    // Execute logic if x equals 5
} else if (x > 7) {
    // Execute logic if x greater than 7
} else {
    // Execute logic in all other cases
}

The condition of an if statement must be of type boolean. Java has no concept of truthy values.

Instructions

In this exercise you'll be writing code to analyze the production of an assembly line in a car factory. The assembly line's speed can range from 0 (off) to 10 (maximum).

At its lowest speed (1), 221 cars are produced each hour. The production increases linearly with the speed. So with the speed set to 4, it should produce 4 * 221 = 884 cars per hour. However, higher speeds increase the likelihood that faulty cars are produced, which then have to be discarded. The following table shows how speed influences the success rate:

  • 1 to 4: 100% success rate.
  • 5 to 8: 90% success rate.
  • 9: 80% success rate.
  • 10: 77% success rate.

You have two tasks.

1. Calculate the production rate per hour

Implement the CarsAssemble.productionRatePerHour() method to calculate the assembly line's production rate per hour, taking into account its current assembly line's speed :

CarsAssemble.productionRatePerHour(6)
// => 1193.4

Note that the value returned is a double.

2. Calculate the number of working items produced per minute

Implement the CarsAssemble.workingItemsPerMinute() method to calculate how many working cars are produced per minute:

CarsAssemble.workingItemsPerMinute(6)
// => 19

Note that the value returned is an int.

Source

Created by

  • @TalesDias