JavaParser: Java Code Generation

In this article, I’m going to show you how to generate Java code using theJavaParser.

Looking to learn more about using the JavaParser in your projects?

I couldn’t find much of the documentation available with regards to code generation in javaparser.org or the manual. So, I thought putting this out would help someone who would like to experiment with the Java parser.

In its simplest form, the JavaParser library allows you to interact with Java source code as a Java object representation in a Java environment. More formally, we refer to this object representation as an Abstract Syntax Tree (AST). Also, it has the ability to manipulate the underlying structure of the source code. This can then be written to a file, providing developers with the facility to build their own code generating software.

First up, you have to instantiate the compilation unit, upon which you will add the remaining pieces of the code.

CompilationUnit compilationUnit = new CompilationUnit();

Then, you can add your import statements to the compilation unit, here:

compilationUnit.addImport("org.springframework.boot.SpringApplication");

You can add your package statement to the compilation unit, as shown below:

compilationUnit.setPackageDeclaration("com.abc.def");

You can add the class declaration to the Java file:

ClassOrInterfaceDeclaration classDeclaration = compilationUnit.addClass("AnyClassName").setPublic(true);

If you want to add annotations at the class level, you can use the following code:

classDeclaration.addAnnotation("AnyAnnotation");

You can add method declarations within your newly declared class, as shown below:

MethodDeclaration methodDeclaration = classDeclaration.addMethod("anyMethodName", PUBLIC);
methodDeclaration.setType("AnyReturnType");

You can add arguments to your newly created method declaration:

methodDeclaration.addAndGetParameter(String.class, "args").setVarArgs(true);

Add annotations on top of the newly declared method:

methodDeclaration.addAndGetAnnotation("AnyAnnotation");

To add the method logic/block statement within the newly declared method, use the below code:

BlockStmt blockStmt = new BlockStmt();
methodDeclaration.setBody(blockStmt);

To declare and instantiate a variable within the method/block statement, use the following code:

ExpressionStmt expressionStmt = new ExpressionStmt();
VariableDeclarationExpr variableDeclarationExpr = new VariableDeclarationExpr();
VariableDeclarator variableDeclarator = new VariableDeclarator();
variableDeclarator.setName("anyVariableName");
variableDeclarator.setType(new ClassOrInterfaceType("AnyVariableType"));
variableDeclarator.setInitializer("new AnyVariableType()");
NodeList<VariableDeclarator> variableDeclarators = new NodeList<>();
variableDeclarators.add(variableDeclarator);
variableDeclarationExpr.setVariables(variableDeclarators);
expressionStmt.setExpression(variableDeclarationExpr);

blockStmt.addStatement(expressionStmt);

To invoke a method of the new variable created within the method/block statement, use the below code:

NameExpr nameExpr = new NameExpr("anyVariableName");
MethodCallExpr methodCallExpr = new MethodCallExpr(nameExpr, "anyMethodName");
methodCallExpr.addArgument("anyArgument");

blockStmt.addStatement(methodCallExpr);

To return the variable created in the method, use the code below:

ReturnStmt returnStmt = new ReturnStmt();
NameExpr returnNameExpr = new NameExpr();
returnNameExpr.setName("anyVariableName");
returnStmt.setExpression(returnNameExpr);

blockStmt.addStatement(returnStmt);

To print the code generated above, just call the toString method of the compilation unit:

String code = compilationUnit.toString();

To add an annotation with multi-valued key value pairs, use the below code.

NodeList<Expression> annotationParamValueList = new NodeList<>();
annotationParamValueList.add(new StringLiteralExpr("Value1");
annotationParamValueList.add(new StringLiteralExpr("Value2");
ArrayInitializerExpr annotationParamValueArrayInitializerExpr = new ArrayInitializerExpr(annotationParamValueList);
Name annotationName = new Name("AnyAnnotationName");
NodeList<MemberValuePair> annotationParamList = new NodeList<>();
MemberValuePair memberValuePair = new MemberValuePair();
memberValuePair.setName(new SimpleName("AnyValue"));
memberValuePair.setValue(annotationParamValueArrayInitializerExpr);
annotationParamList.add(memberValuePair);
AnnotationExpr annotationExpr = new NormalAnnotationExpr(annotationName, annotationParamList);

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Guidelines for Java Code Reviews

Get a jump-start on your next code review session with this list.

Having another pair of eyes scan your code is always useful and helps you spot mistakes before you break production. You need not be an expert to review someone’s code. Some experience with the programming language and a review checklist should help you get started. We’ve put together a list of things you should keep in mind when you’re reviewing Java code. Read on!

1. Follow Java Code Conventions

2. Replace Imperative Code With Lambdas and Streams

3. Beware of the NullPointerException

4. Directly Assigning References From Client Code to a Field

5. Handle Exceptions With Care

…

#java #code quality #java tutorial #code analysis #code reviews #code review tips #code analysis tools #java tutorial for beginners #java code review

How to Install OpenJDK 11 on CentOS 8

What is OpenJDK?

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.

#tutorials #alternatives #centos #centos 8 #configuration #dnf #frameworks #java #java development kit #java ee #java environment variables #java framework #java jdk #java jre #java platform #java sdk #java se #jdk #jre #open java development kit #open source #openjdk #openjdk 11 #openjdk 8 #openjdk runtime environment

12 Common Java Mistakes Made by Newcomers

Everyone makes mistakes, not just beginners, but even professionals. This article goes over a dozen common mistakes that Java newbies and newcomers make and how to avoid them. Have you or your colleagues made any of these common Java mistakes early in your career?

Everyone makes mistakes, not only learners or beginners but professionals. As a programming course, the CodeGym team often collects mistakes of newbies to improve our auto validator. This time we decided to interview experienced programmers about mistakes in Java they made closer to their careers start or noticed them among their young colleagues.

We collected their answers and compiled this list of dozen popular mistakes Java beginners make. The order of errors is random and does not carry any special meaning.

#java #learn-java #java-programming #beginners #beginners-to-coding #learning-to-code #learn-to-code #learn-to-code-java

Going Beyond Java 8: Local Variable Type Inference (var) - DZone Java

According to some surveys, such as JetBrains’s great survey, Java 8 is currently the most used version of Java, despite being a 2014 release.

What you are reading is one in a series of articles titled ‘Going beyond Java 8,’ inspired by the contents of my book, Java for Aliens. These articles will guide you step-by-step through the most important features introduced to the language, starting from version 9. The aim is to make you aware of how important it is to move forward from Java 8, explaining the enormous advantages that the latest versions of the language offer.

In this article, we will talk about the most important new feature introduced with Java 10. Officially called local variable type inference, this feature is better known as the **introduction of the word **var. Despite the complicated name, it is actually quite a simple feature to use. However, some observations need to be made before we can see the impact that the introduction of the word var has on other pre-existing characteristics.

#java #java 11 #java 10 #java 12 #var #java 14 #java 13 #java 15 #verbosity

New to Java? Here Are Some Resources

If you’re looking to learn how to code in Java, you should be taking advantage of these resources. Whatever your preferred style of learning, there is something here for you.

In this tweet, I was asked if I had a list of resources for developers who are new to Java. I didn’t at the time, but I’ve spent some time researching, and here is that list.

I’ve listed content that is both free and paid. It’s not that one type is superior; it’s just to give you plenty of choices. These are the resources that I’ve used and do still use to re-learn Java. So, if you’re new to Java or looking to pick it up again after a break, this blog is for you.

The other super important point is that everyone learns differently; some like reading, some like doing, some like watching, and most of us like a bit of a mix of everything. I tend to switch between them depending on what I want to learn about and how I feel. You’re probably similar, so pick an approach that works for you.

#java #coding basics #java for beginners #coding bootcamp #learning to code #java resources #java bootcamp