BAEL2489 - Avoid check for null statement in Java

core-java/pom.xml

@@ -129,6 +129,13 @@
             <scope>system</scope>
             <systemPath>${java.home}/../lib/tools.jar</systemPath>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations</artifactId>
+            <version>${intellij.annotations.version}</version>
+        </dependency>
+
+
     </dependencies>
 
     <build>
@@ -209,7 +216,8 @@
                         <configuration>
                             <shadedArtifactAttached>true</shadedArtifactAttached>
                             <transformers>
-                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                <transformer
+                                        implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                     <mainClass>org.baeldung.executable.ExecutableMavenJar</mainClass>
                                 </transformer>
                             </transformers>
@@ -264,12 +272,12 @@
                         <argument>-Xmx300m</argument>
                         <argument>-XX:+UseParallelGC</argument>
                         <argument>-classpath</argument>
-                        <classpath />
+                        <classpath/>
                         <argument>com.baeldung.outofmemoryerror.OutOfMemoryGCLimitExceed</argument>
                     </arguments>
                 </configuration>
             </plugin>
-            
+
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
@@ -330,7 +338,7 @@
                                     <executable>java</executable>
                                     <arguments>
                                         <argument>-classpath</argument>
-                                        <classpath />
+                                        <classpath/>
                                         <argument>org.openjdk.jmh.Main</argument>
                                         <argument>.*</argument>
                                     </arguments>
@@ -363,7 +371,8 @@
                                         <manifest>
                                             <addClasspath>true</addClasspath>
                                         </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF
+                                        </manifestFile>
                                     </archive>
 
                                     <includes>
@@ -397,12 +406,14 @@
                                         <manifest>
                                             <addClasspath>true</addClasspath>
                                         </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF
+                                        </manifestFile>
                                     </archive>
 
                                     <includes>
                                         <include>com/baeldung/instrumentation/application/MyAtm.class</include>
-                                        <include>com/baeldung/instrumentation/application/MyAtmApplication.class</include>
+                                        <include>com/baeldung/instrumentation/application/MyAtmApplication.class
+                                        </include>
                                         <include>com/baeldung/instrumentation/application/Launcher.class</include>
                                     </includes>
                                 </configuration>
@@ -432,12 +443,14 @@
                                         <manifest>
                                             <addClasspath>true</addClasspath>
                                         </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF
+                                        </manifestFile>
                                     </archive>
 
                                     <includes>
                                         <include>com/baeldung/instrumentation/agent/AtmTransformer.class</include>
-                                        <include>com/baeldung/instrumentation/agent/MyInstrumentationAgent.class</include>
+                                        <include>com/baeldung/instrumentation/agent/MyInstrumentationAgent.class
+                                        </include>
                                     </includes>
                                 </configuration>
                             </execution>
@@ -449,7 +462,7 @@
     </profiles>
 
     <properties>
-        
+
         <!-- marshalling -->
         <gson.version>2.8.2</gson.version>
 
@@ -470,12 +483,12 @@
 
         <!-- maven plugins -->
         <maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
-        
+
         <javamoney.moneta.version>1.1</javamoney.moneta.version>
         <h2database.version>1.4.197</h2database.version>
         <esapi.version>2.1.0.1</esapi.version>
         <jmh-core.version>1.19</jmh-core.version>
-       
+
         <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
         <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
         <maven-jar-plugin.version>3.0.2</maven-jar-plugin.version>
@@ -486,7 +499,8 @@
         <icu4j.version>61.1</icu4j.version>
         <!-- instrumentation -->
         <javaassist.version>3.21.0-GA</javaassist.version>
-        
+
         <sun.tools.version>1.8.0</sun.tools.version>
+        <intellij.annotations.version>16.0.2</intellij.annotations.version>
     </properties>
 </project>

core-java/src/main/java/com/baeldung/nulls/APIContracts.java

@@ -0,0 +1,29 @@
+package com.baeldung.nulls;
+
+public class APIContracts {
+
+    /**
+     * Prints the value of {@code param} if not null. Prints {@code null} otherwise.
+     * @param param
+     */
+    public void print(Object param) {
+        System.out.println("Printing " + param);
+    }
+
+    /**
+     *
+     * @return non null result
+     * @throws Exception - if result is null
+     */
+    public Object process() throws Exception {
+        Object result = doSomething();
+        if (result == null)
+            throw new Exception("Processing fail. Got a null response");
+        else
+            return result;
+    }
+
+    private Object doSomething() {
+        return null;
+    }
+}

core-java/src/main/java/com/baeldung/nulls/Assertions.java

@@ -0,0 +1,13 @@
+package com.baeldung.nulls;
+
+public class Assertions {
+    
+    public void accept(Object param){
+        assert param != null;
+        
+        doSomething(param);
+    }
+
+    private void doSomething(Object param) {
+    }
+}

core-java/src/main/java/com/baeldung/nulls/EmptyCollections.java

@@ -0,0 +1,24 @@
+package com.baeldung.nulls;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class EmptyCollections {
+
+    public List<String> names(){
+        if (userExist())
+            return Stream.of(readName()).collect(Collectors.toList());
+        else
+            return Collections.emptyList();
+    }
+
+    private boolean userExist() {
+        return false;
+    }
+
+    private String readName() {
+        return "test";
+    }
+}

core-java/src/main/java/com/baeldung/nulls/FindBugsAnnotations.java

@@ -0,0 +1,28 @@
+package com.baeldung.nulls;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+public class FindBugsAnnotations {
+
+    public void accept(@Nonnull Object param) {
+        System.out.println(param.toString());
+    }
+
+    public void print(@Nullable Object param) {
+        System.out.println("Printing " + param);
+    }
+
+    @Nonnull
+    public Object process() throws Exception {
+        Object result = doSomething();
+        if (result == null)
+            throw new Exception("Processing fail. Got a null response");
+        else
+            return result;
+    }
+
+    private Object doSomething() {
+        return null;
+    }
+}

core-java/src/main/java/com/baeldung/nulls/Preconditions.java

@@ -0,0 +1,32 @@
+package com.baeldung.nulls;
+
+public class Preconditions {
+
+    public void goodAccept(String one, String two, String three) {
+        if (null == one || null == two || three == null)
+            throw new IllegalArgumentException();
+    }
+
+    public void badAccept(String one, String two, String three){
+        if (null == one)
+            throw new IllegalArgumentException();
+        else
+            process(one);
+
+        if (null == two)
+            throw new IllegalArgumentException();
+        else
+            process(two);
+
+        if (null == three)
+            throw new IllegalArgumentException();
+        else
+            process(three);
+
+    }
+
+    private void process(String one) {
+    }
+
+
+}

core-java/src/main/java/com/baeldung/nulls/PrimitivesAndWrapper.java

@@ -0,0 +1,24 @@
+package com.baeldung.nulls;
+
+public class PrimitivesAndWrapper {
+
+    public static int sum(int a, int b) {
+        return a + b;
+    }
+
+    public static Integer sum(Integer a, Integer b) {
+        return a + b;
+    }
+
+    public static Integer goodSum(Integer a, Integer b) {
+        if (a != null && b != null)
+            return a + b;
+        else
+            throw new IllegalArgumentException();
+    }
+
+    public static void main(String[] args) {
+        sum(0, 0);
+        sum(null, null);
+    }
+}

core-java/src/main/java/com/baeldung/nulls/UsingLombok.java

@@ -0,0 +1,10 @@
+package com.baeldung.nulls;
+
+import lombok.NonNull;
+
+public class UsingLombok {
+
+    public void accept(@NonNull Object param){
+        System.out.println(param);
+    }
+}

core-java/src/main/java/com/baeldung/nulls/UsingObjects.java

@@ -0,0 +1,24 @@
+package com.baeldung.nulls;
+
+import java.util.Objects;
+
+public class UsingObjects {
+
+    private String checked;
+
+    public void accept(Object param) {
+        try {
+            Objects.requireNonNull(param);
+        } catch (NullPointerException e) {
+            //doSomethingElseToo
+            e.printStackTrace();
+        }
+    }
+
+    public void caller() throws Exception {
+        if (Objects.nonNull(checked))
+            accept(checked);
+        else
+            throw new Exception();
+    }
+}

core-java/src/main/java/com/baeldung/nulls/UsingOptional.java

@@ -0,0 +1,23 @@
+package com.baeldung.nulls;
+
+import java.util.Optional;
+
+public class UsingOptional {
+
+    public Optional<Object> process() {
+        if (isProcessed())
+            return Optional.of("dummy");
+        else
+            return Optional.empty();
+    }
+
+    public void caller() {
+        Optional<Object> result = process();
+        result.ifPresent(p -> System.out.println(p));
+        result.orElseThrow(() -> new IllegalArgumentException());
+    }
+
+    private boolean isProcessed() {
+        return false;
+    }
+}

core-java/src/main/java/com/baeldung/nulls/UsingStringUtils.java

@@ -0,0 +1,17 @@
+package com.baeldung.nulls;
+
+
+import org.apache.commons.lang3.StringUtils;
+
+public class UsingStringUtils {
+
+    public void accept(String param) {
+        if (StringUtils.isNotEmpty(param))
+            System.out.println(param);
+    }
+
+    public void acceptOnlyNonBlank(String param) {
+        if (StringUtils.isNotBlank(param))
+            System.out.println(param);
+    }
+}