| // © 2020 and later: Unicode, Inc. and others. |
| // License & terms of use: http://www.unicode.org/copyright.html |
| |
| |
| package com.ibm.icu.impl.units; |
| |
| |
| import com.ibm.icu.util.Measure; |
| |
| import java.math.BigDecimal; |
| import java.math.RoundingMode; |
| import java.util.ArrayList; |
| import java.util.Collections; |
| import java.util.List; |
| |
| /** |
| * Converts from single or compound unit to single, compound or mixed units. |
| * For example, from `meter` to `foot+inch`. |
| * <p> |
| * DESIGN: |
| * This class uses `UnitConverter` in order to perform the single converter (i.e. converters from a |
| * single unit to another single unit). Therefore, `ComplexUnitsConverter` class contains multiple |
| * instances of the `UnitConverter` to perform the conversion. |
| */ |
| public class ComplexUnitsConverter { |
| public static final BigDecimal EPSILON = BigDecimal.valueOf(Math.ulp(1.0)); |
| public static final BigDecimal EPSILON_MULTIPLIER = BigDecimal.valueOf(1).add(EPSILON); |
| private ArrayList<UnitConverter> unitConverters_; |
| private ArrayList<MeasureUnitImpl> units_; |
| |
| /** |
| * Constructor of `ComplexUnitsConverter`. |
| * NOTE: |
| * - inputUnit and outputUnits must be under the same category |
| * - e.g. meter to feet and inches --> all of them are length units. |
| * |
| * @param inputUnit represents the source unit. (should be single or compound unit). |
| * @param outputUnits represents the output unit. could be any type. (single, compound or mixed). |
| */ |
| public ComplexUnitsConverter(MeasureUnitImpl inputUnit, MeasureUnitImpl outputUnits, |
| ConversionRates conversionRates) { |
| units_ = outputUnits.extractIndividualUnits(); |
| assert (!units_.isEmpty()); |
| |
| // Sort the units in a descending order. |
| Collections.sort( |
| this.units_, |
| Collections.reverseOrder(new MeasureUnitImpl.MeasureUnitImplComparator(conversionRates))); |
| |
| |
| // If the `outputUnits` is `UMEASURE_UNIT_MIXED` such as `foot+inch`. Thus means there is more than one unit |
| // and In this case we need more converters to convert from the `inputUnit` to the first unit in the |
| // `outputUnits`. Then, a converter from the first unit in the `outputUnits` to the second unit and so on. |
| // For Example: |
| // - inputUnit is `meter` |
| // - outputUnits is `foot+inch` |
| // - Therefore, we need to have two converters: |
| // 1. a converter from `meter` to `foot` |
| // 2. a converter from `foot` to `inch` |
| // - Therefore, if the input is `2 meter`: |
| // 1. convert `meter` to `foot` --> 2 meter to 6.56168 feet |
| // 2. convert the residual of 6.56168 feet (0.56168) to inches, which will be (6.74016 |
| // inches) |
| // 3. then, the final result will be (6 feet and 6.74016 inches) |
| unitConverters_ = new ArrayList<>(); |
| for (int i = 0, n = units_.size(); i < n; i++) { |
| if (i == 0) { // first element |
| unitConverters_.add(new UnitConverter(inputUnit, units_.get(i), conversionRates)); |
| } else { |
| unitConverters_.add(new UnitConverter(units_.get(i - 1), units_.get(i), conversionRates)); |
| } |
| } |
| } |
| |
| /** |
| * Returns true if the specified `quantity` of the `inputUnit`, expressed in terms of the biggest |
| * unit in the MeasureUnit `outputUnit`, is greater than or equal to `limit`. |
| * <p> |
| * For example, if the input unit is `meter` and the target unit is `foot+inch`. Therefore, this |
| * function will convert the `quantity` from `meter` to `foot`, then, it will compare the value in |
| * `foot` with the `limit`. |
| */ |
| public boolean greaterThanOrEqual(BigDecimal quantity, BigDecimal limit) { |
| assert !units_.isEmpty(); |
| |
| // NOTE: First converter converts to the biggest quantity. |
| return unitConverters_.get(0).convert(quantity).multiply(EPSILON_MULTIPLIER).compareTo(limit) >= 0; |
| } |
| |
| /** |
| * Returns outputMeasures which is an array with the corresponding values. |
| * - E.g. converting meters to feet and inches. |
| * 1 meter --> 3 feet, 3.3701 inches |
| * NOTE: |
| * the smallest element is the only element that could have fractional values. And all |
| * other elements are floored to the nearest integer |
| */ |
| public List<Measure> convert(BigDecimal quantity) { |
| List<Measure> result = new ArrayList<>(); |
| |
| for (int i = 0, n = unitConverters_.size(); i < n; ++i) { |
| quantity = (unitConverters_.get(i)).convert(quantity); |
| |
| if (i < n - 1) { |
| // The double type has 15 decimal digits of precision. For choosing |
| // whether to use the current unit or the next smaller unit, we |
| // therefore nudge up the number with which the thresholding |
| // decision is made. However after the thresholding, we use the |
| // original values to ensure unbiased accuracy (to the extent of |
| // double's capabilities). |
| BigDecimal newQuantity = quantity.multiply(EPSILON_MULTIPLIER).setScale(0, RoundingMode.FLOOR); |
| |
| result.add(new Measure(newQuantity, units_.get(i).build())); |
| |
| // Keep the residual of the quantity. |
| // For example: `3.6 feet`, keep only `0.6 feet` |
| quantity = quantity.subtract(newQuantity); |
| if (quantity.compareTo(BigDecimal.ZERO) == -1) { |
| quantity = BigDecimal.ZERO; |
| } |
| } else { // LAST ELEMENT |
| result.add(new Measure(quantity, units_.get(i).build())); |
| } |
| } |
| |
| return result; |
| } |
| } |