VarHandles

core-java-9/src/test/java/com/baeldung/java9/varhandles/VariableHandlesTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.java9.varhandles;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.VarHandle;
+
+public class VariableHandlesTest {
+    public int publicTestVariable = 1;
+    private int privateTestVariable = 1;
+    public int variableToSet = 1;
+    public int variableToCompareAndSet = 1;
+    public int variableToGetAndAdd = 0;
+    public byte variableToBitwiseOr = 0;
+    @Test
+    public void whenVariableHandleForPublicVariableIsCreated_ThenItIsInitializedProperly()
+            throws NoSuchFieldException, IllegalAccessException {
+        VarHandle publicIntHandle = MethodHandles.lookup()
+                .in(VariableHandlesTest.class)
+                .findVarHandle(VariableHandlesTest.class,"publicTestVariable", int.class);
+        Assert.assertEquals(1, publicIntHandle.coordinateTypes().size());
+        Assert.assertEquals(VariableHandlesTest.class, publicIntHandle.coordinateTypes().get(0));
+
+    }
+
+    @Test
+    public void whenVariableHandleForPrivateVariableIsCreated_ThenItIsInitializedProperly()
+            throws NoSuchFieldException, IllegalAccessException {
+        VarHandle privateIntHandle = MethodHandles.privateLookupIn(VariableHandlesTest.class, MethodHandles.lookup())
+                .findVarHandle(VariableHandlesTest.class,"privateTestVariable", int.class);
+        Assert.assertNotNull(privateIntHandle);
+        Assert.assertEquals(1, privateIntHandle.coordinateTypes().size());
+        Assert.assertEquals(VariableHandlesTest.class, privateIntHandle.coordinateTypes().get(0));
+
+    }
+
+    @Test
+    public void whenVariableHandleForArrayVariableIsCreated_ThenItIsInitializedProperly()
+            throws NoSuchFieldException, IllegalAccessException {
+        VarHandle arrayVarHandle = MethodHandles.arrayElementVarHandle(int[].class);
+        Assert.assertEquals(2, arrayVarHandle.coordinateTypes().size());
+        Assert.assertEquals(int[].class, arrayVarHandle.coordinateTypes().get(0));
+    }
+
+    @Test
+    public void givenVarHandle_whenGetIsInvoked_ThenValueOfVariableIsReturned() throws NoSuchFieldException, IllegalAccessException {
+            VarHandle publicIntHandle = MethodHandles.lookup()
+                    .in(VariableHandlesTest.class)
+                    .findVarHandle(VariableHandlesTest.class,"publicTestVariable", int.class);
+            Assert.assertEquals(1, publicIntHandle.get(this));
+    }
+
+    @Test
+    public void givenVarHandle_whenSetIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
+        VarHandle publicIntHandle = MethodHandles.lookup()
+                .in(VariableHandlesTest.class)
+                .findVarHandle(VariableHandlesTest.class,"variableToSet", int.class);
+        publicIntHandle.set(this, 15);
+        Assert.assertEquals(15, publicIntHandle.get(this));
+    }
+
+    @Test
+    public void givenVarHandle_whenCompareAndSetIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
+        VarHandle publicIntHandle = MethodHandles.lookup()
+                .in(VariableHandlesTest.class)
+                .findVarHandle(VariableHandlesTest.class,"variableToCompareAndSet", int.class);
+        publicIntHandle.compareAndSet(this, 1,100);
+        Assert.assertEquals(100, publicIntHandle.get(this));
+    }
+
+    @Test
+    public void givenVarHandle_whenGetAndAddIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
+        VarHandle publicIntHandle = MethodHandles.lookup()
+                .in(VariableHandlesTest.class)
+                .findVarHandle(VariableHandlesTest.class,"variableToGetAndAdd", int.class);
+        int before = (int) publicIntHandle.getAndAdd(this, 200);
+        Assert.assertEquals(0, before);
+        Assert.assertEquals(200, publicIntHandle.get(this));
+    }
+
+    @Test
+    public void givenVarHandle_whenGetAndBitwiseOrIsInvoked_ThenValueOfVariableIsChanged() throws NoSuchFieldException, IllegalAccessException {
+        VarHandle publicIntHandle = MethodHandles.lookup()
+                .in(VariableHandlesTest.class)
+                .findVarHandle(VariableHandlesTest.class,"variableToBitwiseOr", byte.class);
+        byte before = (byte) publicIntHandle.getAndBitwiseOr(this, (byte) 127);
+        Assert.assertEquals(0, before);
+        Assert.assertEquals(127, variableToBitwiseOr);
+    }
+}