Adding Super Type Token

alimate · alimate · commit cd51a8c8d0c8 · 2020-05-21T21:25:37.000+04:30
diff --git a/core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/supertype/TypeReference.java b/core-java-modules/core-java-lang-oop-generics/src/main/java/com/baeldung/supertype/TypeReference.java
@@ -0,0 +1,18 @@
+package com.baeldung.supertype;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+
+public abstract class TypeReference<T> {
+
+    private final Type type;
+
+    public TypeReference() {
+        Type superclass = getClass().getGenericSuperclass();
+        type = ((ParameterizedType) superclass).getActualTypeArguments()[0];
+    }
+
+    public Type getType() {
+        return type;
+    }
+}
diff --git a/core-java-modules/core-java-lang-oop-generics/src/test/java/com/baeldung/supertype/TypeReferenceUnitTest.java b/core-java-modules/core-java-lang-oop-generics/src/test/java/com/baeldung/supertype/TypeReferenceUnitTest.java
@@ -0,0 +1,24 @@
+package com.baeldung.supertype;
+
+import org.junit.Test;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class TypeReferenceUnitTest {
+
+    @Test
+    public void givenGenericToken_whenUsingSuperTypeToken_thenPreservesTheTypeInfo() {
+        TypeReference<Map<String, Integer>> token = new TypeReference<Map<String, Integer>>() {};
+        Type type = token.getType();
+
+        assertEquals("java.util.Map<java.lang.String, java.lang.Integer>", type.getTypeName());
+
+        Type[] typeArguments = ((ParameterizedType) type).getActualTypeArguments();
+        assertEquals("java.lang.String", typeArguments[0].getTypeName());
+        assertEquals("java.lang.Integer", typeArguments[1].getTypeName());
+    }
+}
