ScaleUtils.java

public class ScaleUtils {
    private ScaleUtils() {
    }

    public static double linearMap(double source, double sourceMin, double sourceMax, double targetMin, double targetMax) {
        return ((source - sourceMin) / (sourceMax - sourceMin)) * (targetMax - targetMin) + targetMin;
    }

//    public static double linearMap(double source, double sourceMin, double sourceMax, double targetMin, double targetMax) {
//        return normalizedToScale(normalizeScale(source, sourceMin, sourceMax), targetMin, targetMax);
//    }

//    public static double normalizeScale(double source, double sourceMin, double sourceMax) {
//        double sourceRange = sourceMax - sourceMin;
//        return (source - sourceMin) / sourceRange;
//    }
//
//    public static double normalizedToScale(double source, double targetMin, double targetMax) {
//        double targetRange = targetMax - targetMin;
//        return (source * targetRange) + targetMin;
//    }
}

ScaleUtilsTest.java

import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class ScaleUtilsTest {

    @Test
    public void linearMap() {
        double result = ScaleUtils.linearMap(25, 0, 100, 0, 0.5);
        assertEquals(0.125, result, 0);
    }

    @Test
    public void linearMapInverted() {
        double result = ScaleUtils.linearMap(25, 100, 0, 0.5, 1);
        assertEquals(0.875, result, 0);
    }

//    @Test
//    public void normalizeScaleNormal() {
//        double result = ScaleUtils.normalizeScale(62.5, 50, 100);
//        assertEquals(0.25, result, 0);
//    }
//
//    @Test
//    public void normalizeScaleInverted() {
//        double result = ScaleUtils.normalizeScale(87.5, 100, 50);
//        assertEquals(0.25, result, 0);
//    }
//
//    @Test
//    public void normalizedToScale() {
//        double result = ScaleUtils.normalizedToScale(0.25, 50, 100);
//        assertEquals(62.5, result, 0);
//    }
//
//    @Test
//    public void normalizedToScaleInverted() {
//        double result = ScaleUtils.normalizedToScale(0.25, 100, 50);
//        assertEquals(87.5, result, 0);
//    }
}