Round percentages

src/main/java/edu/hm/hafner/coverage/Coverage.java

@@ -24,6 +24,7 @@
     @Serial
     private static final long serialVersionUID = -3802318446471137305L;
     private static final String FRACTION_SEPARATOR = "/";
+    private static final String N_A = "n/a";
 
     /**
      * Creates a new {@link Coverage} instance from the provided string representation. The string representation is
@@ -129,7 +130,7 @@
 
     @Override
     public Coverage add(final Value other) {
-        var otherCoverage = ensureSameMetricAndType(other);
+        var otherCoverage = castValue(other);
 
         return new CoverageBuilder().withMetric(getMetric())
                 .withCovered(getCovered() + otherCoverage.getCovered())
@@ -138,15 +139,15 @@
     }
 
     @Override
-    public Fraction delta(final Value other) {
-        var otherCoverage = ensureSameMetricAndType(other);
+    public Difference subtract(final Value other) {
+        ensureSameMetricAndType(other);
 
-        return getCoveredPercentage().subtract(otherCoverage.getCoveredPercentage());
+        return new Difference(getMetric(), asDouble() - other.asDouble());
     }
 
     @Override
     public Coverage max(final Value other) {
-        var otherCoverage = ensureSameMetricAndType(other);
+        var otherCoverage = castValue(other);
         Ensure.that(getTotal() == otherCoverage.getTotal())
                 .isTrue("Cannot compute maximum of coverages %s and %s since total differs",
                         this, other);
@@ -157,8 +158,9 @@
         return otherCoverage;
     }
 
-    private Coverage ensureSameMetricAndType(final Value other) {
-        ensureSameMetric(other);
+    private Coverage castValue(final Value other) {
+        ensureSameMetricAndType(other);
+
         return (Coverage) other; // the type is checked in ensureSameMetric
     }
 
@@ -184,6 +186,37 @@
         return getTotal() > 0;
     }
 
+    @Override
+    public String asText(final Locale locale) {
+        if (isSet()) {
+            return String.format(locale, "%.2f%%", asRounded());
+        }
+        return N_A;
+    }
+
+    @Override
+    public String asInformativeText(final Locale locale) {
+        if (isSet()) {
+            return String.format(locale, "%.2f%% (%d/%d)", asRounded(), getCovered(), getTotal());
+        }
+        return N_A;
+    }
+
+    @Override
+    public int asInteger() {
+        return getCoveredPercentage().toInt();
+    }
+
+    @Override
+    public double asDouble() {
+        return getCoveredPercentage().toDouble();
+    }
+
+    @Override
+    protected String serializeValue() {
+        return String.format(Locale.ENGLISH, "%d/%d", getCovered(), getTotal());
+    }
+
     @Override
     @Generated
     public boolean equals(final Object o) {
@@ -216,8 +249,8 @@
     }
 
     @Override
-    public String asText() {
-        return String.format(Locale.ENGLISH, "%d/%d", getCovered(), getTotal());
+    public double asRounded() {
+        return getCoveredPercentage().toRounded();
     }
 
     /**

src/main/java/edu/hm/hafner/coverage/Difference.java

@@ -0,0 +1,97 @@
+package edu.hm.hafner.coverage;
+
+import java.io.Serial;
+import java.util.Locale;
+
+import org.apache.commons.lang3.math.Fraction;
+
+/**
+ * A leaf in the tree that represents a delta of two {@link Value} instances. Such values are used to show the
+ * delta (i.e., the difference) of two other values. The delta uses a slightly different textual representation than the
+ * plain value: positive values are prefixed with a plus sign, zero is also handled differently.
+ *
+ * @author Ullrich Hafner
+ */
+public class Difference extends Value {
+    @Serial
+    private static final long serialVersionUID = -1115727256219835389L;
+    /** Serialization prefix for delta values. */
+    public static final String DELTA = "Δ";
+
+    /**
+     * Returns a {@code null} object that indicates that no value has been recorded.
+     *
+     * @param metric
+     *         the coverage metric
+     *
+     * @return the {@code null} object
+     */
+    public static Difference nullObject(final Metric metric) {
+        return new Difference(metric, 0);
+    }
+
+    /**
+     * Creates a new leaf with the given value for the specified metric.
+     *
+     * @param metric
+     *         the coverage metric
+     * @param value
+     *         the value to store
+     */
+    public Difference(final Metric metric, final Fraction value) {
+        super(metric, value);
+    }
+
+    /**
+     * Creates a new leaf with the given value for the specified metric.
+     *
+     * @param metric
+     *         the coverage metric
+     * @param value
+     *         the value to store
+     */
+    public Difference(final Metric metric, final double value) {
+        super(metric, value);
+    }
+
+    /**
+     * Creates a new leaf with the given value (a fraction) for the specified metric.
+     *
+     * @param metric
+     *         the coverage metric
+     * @param numerator
+     *         the numerator, i.e., the three in 'three sevenths'
+     * @param denominator
+     *         the denominator, i.ee, the seven in 'three sevenths'
+     */
+    public Difference(final Metric metric, final int numerator, final int denominator) {
+        super(metric, numerator, denominator);
+    }
+
+    /**
+     * Creates a new leaf with the given value for the specified metric.
+     *
+     * @param metric
+     *         the coverage metric
+     * @param value
+     *         the value
+     */
+    public Difference(final Metric metric, final int value) {
+        super(metric, value);
+    }
+
+    @Override
+    public String asText(final Locale locale) {
+        return getMetric().formatDelta(locale, asDouble());
+    }
+
+    @Override
+    public String asInformativeText(final Locale locale) {
+        return getMetric().formatDelta(locale, asDouble());
+    }
+
+    @Override
+    protected String serializeValue() {
+        return DELTA + super.serializeValue();
+    }
+}

src/main/java/edu/hm/hafner/coverage/FileNode.java

@@ -21,7 +21,6 @@
 
 import org.apache.commons.io.FilenameUtils;
 import org.apache.commons.lang3.StringUtils;
-import org.apache.commons.lang3.math.Fraction;
 
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 
@@ -58,7 +57,7 @@ public final class FileNode extends Node {
 
     private final SortedSet<Integer> modifiedLines = new TreeSet<>();
     private final NavigableMap<Integer, Integer> indirectCoverageChanges = new TreeMap<>();
-    private final NavigableMap<Metric, Fraction> coverageDelta = new TreeMap<>();
+    private final NavigableMap<Metric, Value> coverageDelta = new TreeMap<>();
 
     private TreeString relativePath; // @since 0.22.0
 
@@ -536,7 +535,7 @@ public void computeDelta(final FileNode referenceFile) {
         NavigableMap<Metric, Value> referenceCoverage = referenceFile.getMetricsDistribution();
         getMetricsDistribution().forEach((metric, value) -> {
             if (referenceCoverage.containsKey(metric)) {
-                coverageDelta.put(metric, value.delta(referenceCoverage.get(metric)));
+                coverageDelta.put(metric, value.subtract(referenceCoverage.get(metric)));
             }
         });
     }
@@ -550,8 +549,8 @@ public void computeDelta(final FileNode referenceFile) {
      *
      * @return the delta for the specified metric
      */
-    public Fraction getDelta(final Metric metric) {
-        return coverageDelta.getOrDefault(metric, Fraction.ZERO);
+    public Value getDelta(final Metric metric) {
+        return coverageDelta.getOrDefault(metric, Value.nullObject(metric));
     }
 
     /**