Examples for BAEL-423: (#2103)

* Examples for BAEL-423:

Handling Exceptions in Lambda Expression with Vavr(Javaslang)

* Modified Lifting and Try API examples and removed Validation API examples

vavr/src/test/java/com/baeldung/vavr/exception/handling/VavrExceptionHandlingUnitTest.java

@@ -0,0 +1,84 @@
+package com.baeldung.vavr.exception.handling;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import io.vavr.API;
+import io.vavr.CheckedFunction1;
+
+public class VavrExceptionHandlingUnitTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(VavrExceptionHandlingUnitTest.class);
+    
+    private List<Integer> integers;
+    private List<Integer> validIntegersOnly;
+
+    @Before
+    public void init() {
+        integers = Arrays.asList(3, 9, 7, 0, 10, 20);
+        validIntegersOnly = Arrays.asList(3, 9, 7, 5, 10, 20);
+    }
+
+    @Test
+    public void exceptionCausingMethod_UsingCheckedFunction_ThenSuccess() {
+    	CheckedFunction1<Integer, Integer> fn = i -> readFromFile(i);
+    	    	    
+    	validIntegersOnly.stream().map(fn.unchecked()).forEach(i -> LOG.debug("{}", i));
+    }
+    
+    @Test(expected = IOException.class)
+    public void exceptionCausingMethod_UsingCheckedFunction_ThenFailure() {
+    	CheckedFunction1<Integer, Integer> fn = i -> readFromFile(i);
+    	    	    
+    	integers.stream().map(fn.unchecked()).forEach(i -> LOG.debug("{}", i));
+    }
+    
+    @Test
+    public void exceptionCausingMethod_UsingAPI_ThenSuccess() {
+    	validIntegersOnly.stream().map(API.unchecked(i -> readFromFile(i))).forEach(i -> LOG.debug("{}", i));
+    }
+
+    @Test(expected = IOException.class)
+    public void exceptionCausingMethod_UsingAPI_ThenFailure() {
+    	integers.stream().map(API.unchecked(i -> readFromFile(i))).forEach(i -> LOG.debug("{}", i));
+    }
+
+    @Test
+    public void exceptionCausingMethod_UsingLift_ThenSuccess() {
+    	validIntegersOnly.stream().map(CheckedFunction1.lift(i -> readFromFile(i)))
+    		.map(i -> i.getOrElse(-1))
+    		.forEach(i -> {Assert.assertNotSame(-1, i);LOG.debug("{}", i);});
+    }
+    
+    @Test
+    public void exceptionCausingMethod_UsingLift_ThenFailure() {
+    	integers.stream().map(CheckedFunction1.lift(i -> readFromFile(i)))
+    		.map(i -> i.getOrElse(-1))
+    		.forEach(i -> LOG.debug("{}", i));
+    	    
+    }
+    
+    @Test
+    public void exceptionCausingMethod_UsingTry_ThenSuccess() {
+    	
+    	integers.stream().map(CheckedFunction1.liftTry(i -> readFromFile(i)))
+    					.map(i -> i.onFailure(e -> Assert.assertTrue(e instanceof IOException)))
+    					.map(i -> i.onSuccess(e -> LOG.debug("{}", e)))
+    					.forEach(i -> {});
+    }
+
+    private static Integer readFromFile(Integer i) throws IOException {
+        if (i == 0) {
+            throw new IOException(); // mock IOException
+        }
+        return i * i;
+    }
+    
+}