Converter.java class file from the Stackskills complete Android Marshmallow series since Mohitd didn't provide it!

Converter.java

// CHANGE THIS TO YOUR PACKAGE NAME!
package com.tmlov.unitconverter;

public class Converter {
    public enum Unit {
        INCH,
        CENTIMETER,
        FOOT,
        YARD,
        METER,
        MILE,
        KILOMETER;

        public static Unit fromString(String text) {
            if (text != null) {
                for (Unit unit : Unit.values()) {
                    if (text.equalsIgnoreCase(unit.toString())) {
                        return unit;
                    }
                }
            }
            throw new IllegalArgumentException("Cannot find a value for " + text);
        }
    }

    private final double multiplier;

    public Converter(Unit from, Unit to) {
        double constant = 1;
        switch (from) {
            case INCH:
                if (to == Unit.CENTIMETER) {
                    constant = 2.54;
                } else if (to == Unit.FOOT) {
                    constant = 0.0833333;
                } else if (to == Unit.YARD) {
                    constant = 0.0277778;
                } else if (to == Unit.METER) {
                    constant = 0.254;
                } else if (to == Unit.MILE) {
                    constant = 1.5783e-5;
                } else if (to == Unit.KILOMETER) {
                    constant = 2.54e-5;
                }
                break;
            case CENTIMETER:
                if (to == Unit.INCH) {
                    constant = 0.393701;
                } else if (to == Unit.FOOT) {
                    constant = 0.0328084;
                } else if (to == Unit.YARD) {
                    constant = 0.0109361;
                } else if (to == Unit.METER) {
                    constant = 0.01;
                } else if (to == Unit.MILE) {
                    constant = 6.2137e-6;
                } else if (to == Unit.KILOMETER) {
                    constant = 1e-5;
                }
                break;
            case FOOT:
                if (to == Unit.INCH) {
                    constant = 12;
                } else if (to == Unit.CENTIMETER) {
                    constant = 30.48;
                } else if (to == Unit.YARD) {
                    constant = 0.333333;
                } else if (to == Unit.METER) {
                    constant = 0.3048;
                } else if (to == Unit.MILE) {
                    constant = 0.000189394;
                } else if (to == Unit.KILOMETER) {
                    constant = 0.0003048;
                }
                break;
            case YARD:
                if (to == Unit.INCH) {
                    constant = 36;
                } else if (to == Unit.CENTIMETER) {
                    constant = 91.44;
                } else if (to == Unit.FOOT) {
                    constant = 3;
                } else if (to == Unit.METER) {
                    constant = 3;
                } else if (to == Unit.MILE) {
                    constant = 0.000568182;
                } else if (to == Unit.KILOMETER) {
                    constant = 0.0009144;
                }
                break;
            case METER:
                if (to == Unit.INCH) {
                    constant = 39.3701;
                } else if (to == Unit.CENTIMETER) {
                    constant = 100;
                } else if (to == Unit.FOOT) {
                    constant = 3.28084;
                } else if (to == Unit.YARD) {
                    constant = 1.09361;
                } else if (to == Unit.MILE) {
                    constant = 0.000621371;
                } else if (to == Unit.KILOMETER) {
                    constant = 0.001;
                }
                break;
            case MILE:
                if (to == Unit.INCH) {
                    constant = 63360;
                } else if (to == Unit.CENTIMETER) {
                    constant = 160934;
                } else if (to == Unit.FOOT) {
                    constant = 5280;
                } else if (to == Unit.YARD) {
                    constant = 1760;
                } else if (to == Unit.METER) {
                    constant = 1609.34;
                } else if (to == Unit.KILOMETER) {
                    constant = 1.60934;
                }
                break;
            case KILOMETER:
                if (to == Unit.INCH) {
                    constant = 39370.1;
                } else if (to == Unit.CENTIMETER) {
                    constant = 100000;
                } else if (to == Unit.FOOT) {
                    constant = 3280.84;
                } else if (to == Unit.YARD) {
                    constant = 1093.61;
                } else if (to == Unit.METER) {
                    constant = 1000;
                } else if (to == Unit.MILE) {
                    constant = 0.612371;
                }
                break;
        }

        multiplier = constant;
    }

    public double convert(double input) { return input * multiplier; }
}