eecs2030.test1

Class Weight

java.lang.Object

eecs2030.test1.Weight

public class Weight
extends Object

A class that represents weights in kilograms or pounds. Every weight has a numeric value and a string representing the units of the weight.

Field Summary

Fields

Modifier and Type	Field and Description
static String	KG The abbreviation of kilogram.
static double	KG_PER_LB The number of kilograms in one pound.
static String	LB The abbreviation of pounds.

Constructor Summary

Constructors

Constructor and Description
Weight() Initializes the weight to 0 kg.
Weight(double wt, String units) Initializes the weight to the given numeric value having the given units.
Weight(Weight other) Initializes the weight by copying the numeric value and units of another weight.

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object obj) Compares two weights for equality.
double	get() Gets the numeric value of the weight using the current units.
String	getUnits() Gets the units of the weight.
void	set(double wt) Sets the numeric value of the weight using the current units.
void	setUnits(String units) Set the units of the weight.
static double	toKilograms(double lb) Converts a value of pounds to the equivalent value of kilograms.
static double	toPounds(double kg) Converts a value of kilograms to the equivalent value of pounds.
String	toString() Returns a string made up of the numeric value of the weight followed by a space followed by its units.

Methods inherited from class java.lang.Object

getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

KG

public static final String KG

The abbreviation of kilogram.

See Also:

Constant Field Values

LB

public static final String LB

The abbreviation of pounds.

See Also:

Constant Field Values

KG_PER_LB

public static final double KG_PER_LB

The number of kilograms in one pound.

See Also:

Constant Field Values

Constructor Detail

Weight

public Weight()

Initializes the weight to 0 kg.

Weight

public Weight(Weight other)

Initializes the weight by copying the numeric value and units of another weight.

Parameters:

other - the weight to copy

Weight

public Weight(double wt,
              String units)

Initializes the weight to the given numeric value having the given units.

Parameters:

wt - the weight

units - the units (Weight.KG or Weight.LB)

Throws:

IllegalArgumentException - if the weight is less than zero

IllegalArgumentException - if units is not one of Weight.KG or Weight.LB

Precondition:

wt greater than or equal to zero, units equal to Weight.KG or Weight.LB

Method Detail

get

public double get()

Gets the numeric value of the weight using the current units. For instance, the value of kg is 1.5 and the value of lb is 5.2 in the following example:

 Weight w = new Weight(1.5, Weight.KG);
 double kg = w.get();
 
 Weight u = new Weight(5.2, Weight.LB);
 double lb = u.get();
 

Returns:

the numeric value of the weight using the current units

set

public final void set(double wt)

Sets the numeric value of the weight using the current units. For instance, the final numeric value of w is 15.0 kilograms in the example below:

 Weight w = new Weight(0, Weight.KG);
 w.set(15.0);
 

Parameters:

wt - the numeric value of the weight

Throws:

IllegalArgumentException - if the weight is less than zero

Precondition:

wt greater than or equal to zero

getUnits

public String getUnits()

Gets the units of the weight.

Returns:

Weight.KG if the weight is in kilograms, or Weight.LB if the weight is in pounds.

setUnits

public final void setUnits(String units)

Set the units of the weight. This method has the side effect that the numeric value of the weight changes to reflect the change in units. For instance, changing the units of 1.0 pound to kilograms causes the value of kg to be equal to Weight.KG_PER_LB:

 Weight w = new Weight(1.0, Weight.LB);
 w.setUnits(Weight.KG);
 double kg = t.get();                 // kg is equal to Weight.KG_PER_LB
 String units = t.getUnits();         // units is equal to Weight.KG 
 

Parameters:

units - the units of the weight (Weight.KG or Weight.LB)

Throws:

IllegalArgumentException - if units is not one of Weight.KG or Weight.LB

Precondition:

weight equal to Weight.KG or Weight.LB

toPounds

public static double toPounds(double kg)

Converts a value of kilograms to the equivalent value of pounds. The formula to convert kilograms to pounds is:

LB = KG / Weight.KG_PER_LB

where LB is the weight in pounds and KG is the weight in kilograms.

Parameters:

kg - a weight in kilograms

Returns:

the equivalent value of the weight in pounds

toKilograms

public static double toKilograms(double lb)

Converts a value of pounds to the equivalent value of kilograms. The formula to convert pounds to kilograms is:

KG = LB × Weight.KG_PER_LB

where LB is the weight in pounds and KG is the weight in kilograms.

Parameters:

lb - a weight in pounds

Returns:

the equivalent value of the weight in kilograms

toString

public String toString()

Returns a string made up of the numeric value of the weight followed by a space followed by its units. For example, the Strings

 12.5 kg
 73.01234 lb
 

are returned for weights of 12.5 kilograms and 73.01234 pounds, respectively.

Overrides:

toString in class Object

Returns:

a string representation of the weight

equals

public boolean equals(Object obj)

Compares two weights for equality. Two weights are considered equal if they represent the same weight expressed in kilograms. For instance, the values of eq1 and eq2 are true in the following example:

 Weight w = new Weight(1.0, Weight.LB);               // 1 lb
 Weight u = new Weight(Weight.KG_PER_LB, Weight.KG);  // 0.45359237 kg
 boolean eq1 = w.equals(u);    // true
 boolean eq2 = u.equals(w);    // true
 

because 1.0 pound is equivalent to Weight.KG_PER_LB kilograms, and vice versa.

Overrides:

equals in class Object