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Add new section on instanceof
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‎core-java-modules/core-java-lang-3/src/test/java/com/baeldung/isinstancevsisassignablefrom/IsInstanceIsAssignableFromUnitTest.java‎

Lines changed: 62 additions & 12 deletions
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import org.junit.Test;
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public class IsInstanceIsAssignableFromUnitTest {
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@Test
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public void whenUsingIsInstanceProperly_desiredResultsHappen() {
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public void whenUsingInstanceOfProperly_thenDesiredResultsHappen() {
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Shape shape = new Triangle();
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Triangle triangle = new Triangle();
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IsoscelesTriangle isoscelesTriangle = new IsoscelesTriangle();
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Shape nonspecificShape = null;
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assertTrue(shape instanceof Shape);
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assertTrue(triangle instanceof Shape);
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assertTrue(isoscelesTriangle instanceof Shape);
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assertFalse(nonspecificShape instanceof Shape);
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assertTrue(shape instanceof Triangle);
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assertTrue(triangle instanceof Triangle);
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assertTrue(isoscelesTriangle instanceof Triangle);
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assertFalse(nonspecificShape instanceof Triangle);
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assertFalse(shape instanceof IsoscelesTriangle);
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assertFalse(triangle instanceof IsoscelesTriangle);
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assertTrue(isoscelesTriangle instanceof IsoscelesTriangle);
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assertFalse(nonspecificShape instanceof IsoscelesTriangle);
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}
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@Test
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public void whenUsingIsInstanceProperly_thenDesiredResultsHappen() {
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Shape shape = new Triangle();
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Triangle triangle = new Triangle();
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IsoscelesTriangle isoscelesTriangle = new IsoscelesTriangle();
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Triangle isoscelesTriangle2 = new IsoscelesTriangle();
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Shape nonspecificShape = null;
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assertTrue(Shape.class.isInstance(shape));
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assertTrue(Shape.class.isInstance(triangle));
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assertTrue(Shape.class.isInstance(isoscelesTriangle));
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assertTrue(Shape.class.isInstance(isoscelesTriangle2));
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assertFalse(Shape.class.isInstance(nonspecificShape));
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assertTrue(Triangle.class.isInstance(shape));
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assertTrue(Triangle.class.isInstance(triangle));
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assertTrue(Triangle.class.isInstance(isoscelesTriangle));
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assertTrue(Triangle.class.isInstance(isoscelesTriangle2));
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assertFalse(IsoscelesTriangle.class.isInstance(shape));
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assertFalse(IsoscelesTriangle.class.isInstance(triangle));
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assertTrue(IsoscelesTriangle.class.isInstance(isoscelesTriangle));
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assertTrue(IsoscelesTriangle.class.isInstance(isoscelesTriangle2));
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assertTrue(IsoscelesTriangle.class.isInstance(isoscelesTriangle2));
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}
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@Test
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public void whenUsingIsAssignableFromProperly_desiredResultsHappen() {
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public void whenUsingIsAssignableFromProperly_thenDesiredResultsHappen() {
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Shape shape = new Triangle();
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Triangle triangle = new Triangle();
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IsoscelesTriangle isoscelesTriangle = new IsoscelesTriangle();
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Triangle isoscelesTriangle2 = new IsoscelesTriangle();
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assertFalse(shape.getClass().isAssignableFrom(Shape.class));
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assertTrue(shape.getClass().isAssignableFrom(shape.getClass()));
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assertTrue(shape.getClass().isAssignableFrom(triangle.getClass()));
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assertTrue(shape.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
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assertTrue(shape.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
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assertFalse(triangle.getClass().isAssignableFrom(Shape.class));
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assertTrue(triangle.getClass().isAssignableFrom(shape.getClass()));
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assertTrue(triangle.getClass().isAssignableFrom(triangle.getClass()));
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assertTrue(triangle.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
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assertTrue(triangle.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
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assertFalse(isoscelesTriangle.getClass().isAssignableFrom(Shape.class));
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assertFalse(isoscelesTriangle.getClass().isAssignableFrom(shape.getClass()));
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assertFalse(isoscelesTriangle.getClass().isAssignableFrom(triangle.getClass()));
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assertTrue(isoscelesTriangle.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
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assertTrue(isoscelesTriangle.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
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assertFalse(isoscelesTriangle2.getClass().isAssignableFrom(Shape.class));
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assertFalse(isoscelesTriangle2.getClass().isAssignableFrom(shape.getClass()));
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assertFalse(isoscelesTriangle2.getClass().isAssignableFrom(triangle.getClass()));
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assertTrue(isoscelesTriangle2.getClass().isAssignableFrom(isoscelesTriangle.getClass()));
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assertTrue(isoscelesTriangle2.getClass().isAssignableFrom(isoscelesTriangle2.getClass()));
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}
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@Test(expected = NullPointerException.class)
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public void whenUsingNull_thenDesiredResultsHappen() {
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assertFalse(null instanceof Shape);
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assertFalse(Shape.class.isInstance(null));
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assertFalse(Shape.class.isAssignableFrom(null)); // NullPointerException
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}
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@Test
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public void whenUsingPrimitiveType_thenDesiredResultsHappen() {
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//assertFalse(10 instanceof int); // illegal
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assertFalse(int.class.isInstance(10));
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assertTrue(Integer.class.isInstance(10));
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assertTrue(int.class.isAssignableFrom(int.class));
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assertFalse(float.class.isAssignableFrom(int.class));
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}
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@Test
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public void whenUsingClassInstanceVariable_thenDesiredResultsHappen() {
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Shape shape = new Triangle();
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Triangle triangle = new Triangle();
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Class<?> clazz = shape.getClass();
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//assertFalse(triangle instanceof clazz); // illegal
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assertTrue(clazz.isInstance(triangle));
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assertTrue(clazz.isAssignableFrom(triangle.getClass()));
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}
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}

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