[chk-double-is-int] check if doulbe is integer (#15312)

2023-12-03 17:55:52 +01:00
parent 1bae3d7580
commit 7f1bfe6a87
3 changed files with 121 additions and 1 deletions
@@ -0,0 +1,83 @@
+package com.baeldung.doubleisint;
+
+import com.google.common.math.DoubleMath;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class CheckDoubleIsAnIntegerUnitTest {
+
+    boolean notNaNOrInfinity(double d) {
+        return !(Double.isNaN(d) || Double.isInfinite(d));
+    }
+
+    @Test
+    void whenConvertingToInt_thenGetExpectedResult() {
+        double d1 = 42.0D;
+        boolean d1IsInteger = notNaNOrInfinity(d1) && (int) d1 == d1;
+        assertTrue(d1IsInteger);
+
+        double d2 = 42.42D;
+        boolean d2IsInteger = notNaNOrInfinity(d2) && (int) d2 == d2;
+        assertFalse(d2IsInteger);
+
+        double d3 = 2.0D * Integer.MAX_VALUE;
+        boolean d3IsInteger = notNaNOrInfinity(d3) && (int) d3 == d3;
+        assertTrue(!d3IsInteger); // <-- fails if exceeding Integer's range
+    }
+
+    @Test
+    void whenUsingModuloOperator_thenGetExpectedResult() {
+        double d1 = 42.0D;
+        boolean d1IsInteger = notNaNOrInfinity(d1) && (d1 % 1) == 0;
+        assertTrue(d1IsInteger);
+
+        double d2 = 42.42D;
+        boolean d2IsInteger = notNaNOrInfinity(d2) && (d2 % 1) == 0;
+        assertFalse(d2IsInteger);
+
+        double d3 = 2.0D * Integer.MAX_VALUE;
+        boolean d3IsInteger = notNaNOrInfinity(d3) && (d3 % 1) == 0;
+        assertTrue(d3IsInteger);
+
+    }
+
+
+    @Test
+    void whenCheckingFloorOrCeilingValue_thenGetExpectedResult() {
+        double d1 = 42.0D;
+        boolean d1IsInteger = notNaNOrInfinity(d1) && Math.floor(d1) == d1;
+        assertTrue(d1IsInteger);
+
+        double d2 = 42.42D;
+        boolean d2IsInteger = notNaNOrInfinity(d2) && Math.floor(d2) == d2;
+        assertFalse(d2IsInteger);
+
+        double d3 = 2.0D * Integer.MAX_VALUE;
+        boolean d3IsInteger = notNaNOrInfinity(d3) && Math.floor(d3) == d3;
+        assertTrue(d3IsInteger);
+
+    }
+
+    @Test
+    void whenUsingGuava_thenGetExpectedResult() {
+        double d1 = 42.0D;
+        boolean d1IsInteger = DoubleMath.isMathematicalInteger(d1);
+        assertTrue(d1IsInteger);
+
+        double d2 = 42.42D;
+        boolean d2IsInteger = DoubleMath.isMathematicalInteger(d2);
+        assertFalse(d2IsInteger);
+
+        double d3 = 2.0D * Integer.MAX_VALUE;
+        boolean d3IsInteger = DoubleMath.isMathematicalInteger(d3);
+        assertTrue(d3IsInteger);
+
+        boolean isInfinityInt = DoubleMath.isMathematicalInteger(Double.POSITIVE_INFINITY);
+        assertFalse(isInfinityInt);
+
+        boolean isNanInt = DoubleMath.isMathematicalInteger(Double.NaN);
+        assertFalse(isNanInt);
+    }
+}