Merge pull request #10478 from sk1418/uncheckedCast

unchecked cast warning article

core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/uncheckedcast/UncheckedCast.java

@@ -0,0 +1,26 @@
+package com.baeldung.uncheckedcast;
+
+import java.time.LocalDate;
+import java.time.Month;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
+
+public class UncheckedCast {
+    public static Map getRawMap() {
+        Map rawMap = new HashMap();
+        rawMap.put("date 1", LocalDate.of(2021, Month.FEBRUARY, 10));
+        rawMap.put("date 2", LocalDate.of(1992, Month.AUGUST, 8));
+        rawMap.put("date 3", LocalDate.of(1976, Month.NOVEMBER, 18));
+        return rawMap;
+    }
+
+    public static Map getRawMapWithMixedTypes() {
+        Map rawMap = new HashMap();
+        rawMap.put("date 1", LocalDate.of(2021, Month.FEBRUARY, 10));
+        rawMap.put("date 2", LocalDate.of(1992, Month.AUGUST, 8));
+        rawMap.put("date 3", LocalDate.of(1976, Month.NOVEMBER, 18));
+        rawMap.put("date 4", new Date());
+        return rawMap;
+    }
+}

core-java-modules/core-java-lang-oop-generics/src/test/java/com/baeldung/uncheckedcast/UncheckedCastUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.uncheckedcast;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.time.LocalDate;
+import java.time.Month;
+import java.util.Map;
+
+public class UncheckedCastUnitTest {
+
+    @Test
+    public void givenRawMap_whenCastToTypedMap_shouldHaveCompilerWarning() {
+        Map<String, LocalDate> castFromRawMap = (Map<String, LocalDate>) UncheckedCast.getRawMap();
+        Assert.assertEquals(3, castFromRawMap.size());
+        Assert.assertEquals(castFromRawMap.get("date 2"), LocalDate.of(1992, Month.AUGUST, 8));
+    }
+
+    @Test(expected = ClassCastException.class)
+    public void givenMixTypedRawMap_whenCastToTypedMap_shouldThrowClassCastException() {
+        Map<String, LocalDate> castFromRawMap = (Map<String, LocalDate>) UncheckedCast.getRawMapWithMixedTypes();
+        Assert.assertEquals(4, castFromRawMap.size());
+        Assert.assertTrue(castFromRawMap.get("date 4").isAfter(castFromRawMap.get("date 3")));
+    }
+}