Units.java

package edu.stanford.hci.r3.units;

public abstract class Units implements Cloneable {

        public static final double POINTS_PER_INCH = 72;

        public static Units add(Units a, Units b) {
                return a.getUnitsObjectOfSameTypeWithValue(a.getValue() + b.getValueIn(a));
        }

        public static Units subtract(Units a, Units b) {
                return a.getUnitsObjectOfSameTypeWithValue(a.getValue() - b.getValueIn(a));
        }

        private String unitName;

        private double value;

        protected Units(double val) {
                value = val;
                unitName = getClass().getSimpleName(); // use the java name for the units name
        }

        public Units(double val, String name) {
                value = val;
                unitName = name; // use the custom units name
        }

        protected Units clone() {
                try {
                        return (Units) super.clone();
                } catch (CloneNotSupportedException e) {
                        e.printStackTrace();
                }
                return null;
        }

        @Override
        public boolean equals(Object o) {
                if (o instanceof Units) {
                        final Units other = (Units) o;

                        // if we get our value in the other units, is it equal to the value of the other unit?
                        return getValueIn(other) == other.getValue();
                }
                // not a units object!
                return false;
        }

        public double getConversionTo(Units destUnits) {
                return destUnits.getNumberOfUnitsInOneInch() / getNumberOfUnitsInOneInch();
        }

        public Units getCopy() {
                // tricky, huh? =)
                return getUnitsObjectOfSameLengthIn(this);
        }

        protected abstract double getNumberOfUnitsInOneInch();

        public String getUnitName() {
                return unitName;
        }

        public Units getUnitsObjectOfSameLengthIn(Units destUnits) {
                final Units dest = destUnits.clone();
                dest.value = getValueIn(dest);
                return dest;
        }

        public Units getUnitsObjectOfSameTypeWithValue(double val) {
                final Units dest = this.clone();
                dest.value = val;
                return dest;
        }

        public double getValue() {
                return value;
        }

        public double getValueIn(Units destUnits) {
                return value * getConversionTo(destUnits);
        }

        public double getValueInCentimeters() {
                return getValueIn(Centimeters.ONE);
        }

        public double getValueInInches() {
                return getValueIn(Inches.ONE);
        }

        public double getValueInMillimeters() {
                return getValueIn(Millimeters.ONE);
        }

        public double getValueInPatternDots() {
                return getValueIn(PatternDots.ONE);
        }

        public double getValueInPixels() {
                return getValueIn(Pixels.ONE);
        }

        public double getValueInPoints() {
                return getValueIn(Points.ONE);
        }

        public Inches toInches() {
                return new Inches(getValueInInches());
        }

        public Pixels toPixels() {
                return new Pixels(getValueInPixels());
        }

        public Points toPoints() {
                return new Points(getValueInPoints());
        }

        public String toString() {
                return value + " " + getUnitName();
        }

}

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