Java

Here’s a comprehensive list of Java CLI commands and techniques, including tools and configurations for effective Java development and management.

Java CLI Commands

1. Java Version Management

Check Java version:
```
java -version
```
Check the Java compiler version:
```
javac -version
```

Update Java (using SDKMAN for version management):

sdk install java
sdk list java # List available Java versions
sdk use java <version> # Set a specific Java version

2. Java Compilation and Execution

Compile a Java program:
```
javac HelloWorld.java
```
Run a compiled Java program:
```
java HelloWorld
```
Compile multiple Java files:
```
javac *.java
```
Run a Java program with a specific classpath:
```
java -cp .:lib/* HelloWorld
```
Run a Java program with specific JVM options:
```
java -Xmx512m -Xms256m HelloWorld
```
Compile and run a single-file source-code program:
```
java HelloWorld.java
```

3. Java Package Management

Create a JAR file:
```
jar cvf HelloWorld.jar HelloWorld.class
```
Run a JAR file:
```
java -jar HelloWorld.jar
```
List contents of a JAR file:
```
jar tvf HelloWorld.jar
```
Extract contents of a JAR file:
```
jar xvf HelloWorld.jar
```
Update a JAR file:
```
jar uvf HelloWorld.jar newfile.class
```

4. Java Environment Management

Set environment variables for Java:

export JAVA_HOME=/path/to/java
export PATH=$JAVA_HOME/bin:$PATH

Check the value of JAVA_HOME:
```
echo $JAVA_HOME
```

Configure environment variables in a script:

#!/bin/bash
export JAVA_HOME=/path/to/java
export PATH=$JAVA_HOME/bin:$PATH

5. Java Build Tools

Maven:

Create a new Maven project:

mvn archetype:generate -DgroupId=com.example -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

Build a Maven project:
```
mvn clean install
```

Run a Maven project:

mvn exec:java -Dexec.mainClass="com.example.App"

Add a dependency to a Maven project:

<dependency>
  <groupId>org.example</groupId>
  <artifactId>example-dependency</artifactId>
  <version>1.0.0</version>
</dependency>

Check for updates to project dependencies:
```
mvn versions:display-dependency-updates
```

Gradle:
- Create a new Gradle project:
```
gradle init
```
- Build a Gradle project:
```
gradle build
```
- Run a Gradle project:
```
gradle run
```
- Add a dependency to a Gradle project:
```
dependencies {
  implementation 'org.example:example-dependency:1.0.0'
}
```
- Check for updates to project dependencies:
```
gradle dependencyUpdates
```

6. Java Testing

JUnit:

Run JUnit tests:

java -cp .:junit-4.12.jar org.junit.runner.JUnitCore TestClass

Create a test class (JUnit 4):

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class TestClass {
    @Test
    public void testMethod() {
        assertEquals(1, 1);
    }
}

Create a test class (JUnit 5):

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class TestClass {
    @Test
    public void testMethod() {
        assertEquals(1, 1);
    }
}

Run JUnit 5 tests with Maven:
```
mvn test
```
Run JUnit 5 tests with Gradle:
```
gradle test
```

7. Java Profiling and Debugging

Run Java with a profiler:

java -agentlib:hprof=cpu=samples,heap=sites HelloWorld

Generate a heap dump:

jmap -dump:live,format=b,file=heapdump.hprof <pid>

Analyze a heap dump (using jhat):
```
jhat heapdump.hprof
```

Run a Java program with remote debugging enabled:

java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 HelloWorld

Attach a debugger to a running Java process:
```
jdb -attach 5005
```
Analyze thread dumps:
```
jstack <pid>
```
Analyze CPU usage (using jstat):
```
jstat -gc <pid>
```

8. Java Documentation

Generate Javadoc:
```
javadoc -d doc HelloWorld.java
```
Generate Javadoc for a package:
```
javadoc -d doc com.example.package
```

Generate Javadoc with a custom stylesheet:

javadoc -d doc -stylesheetfile custom.css HelloWorld.java

Advanced Java Techniques

1. Advanced JVM Options

Configure garbage collection logging:
```
java -Xlog:gc* HelloWorld
```
Configure heap size settings:
```
java -Xms512m -Xmx1024m HelloWorld
```

Enable flight recorder:

java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder HelloWorld

Enable just-in-time (JIT) compiler logging:
```
java -XX:+PrintCompilation HelloWorld
```

Run a Java program in headless mode:

java -Djava.awt.headless=true HelloWorld

2. Advanced Build Configurations

Maven profiles for different environments:

<profiles>
  <profile>
    <id>development</id>
    <properties>
      <env>development</env>
    </properties>
  </profile>
  <profile>
    <id>production</id>
    <properties>
      <env>production</env>
    </properties>
  </profile>
</profiles>

Conditional dependency in Maven:

<dependency>
  <groupId>org.example</groupId>
  <artifactId>example-dependency</artifactId>
  <version>1.0.0</version>
  <scope>${env}</scope>
</dependency>

Custom Gradle task:

task hello {
    doLast {
        println 'Hello, Gradle!'
    }
}

Multi-project build in Gradle:
```
include 'project1', 'project2'
```

3. Advanced Testing Techniques

Parameterized tests with JUnit 5:

import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;

public class ParameterizedTestExample {
    @ParameterizedTest
    @ValueSource(strings = {"one", "two", "three"})
    void testWithStringParameter(String argument) {
        assertNotNull(argument);
    }
}

Mocking with Mockito:

import static org.mockito.Mockito.*;
import org.junit.jupiter.api.Test;

public class MockTest {
    @Test
    void testMock() {
        List mockList = mock(List.class);
        when(mockList.size()).thenReturn(10);
        assertEquals(10, mockList.size());
    }
}

Integration tests with springboot:

import org.springframework.beans.factory.annotation.Autowired;

@SpringBootTest
public class ApplicationTests {

    @Autowired
    private SomeService someService;

    @Test
    public void contextLoads() {
        assertNotNull(someService);
    }
}

4. Java Performance Tuning

Using VisualVM for monitoring and profiling:
```
jvisualvm
```
Heap analysis with Eclipse Memory Analyzer (MAT):
```
mat -vmargs -Xmx4G
```
Analyze garbage collection logs with GCViewer:
```
java -jar gcviewer.jar gc.log
```

Configure JVM for low latency:

java -XX:+UseG1GC -XX:MaxGCPauseMillis=100 HelloWorld

Enable and configure JIT compiler optimizations:

java -XX:+AggressiveOpts -XX:+OptimizeStringConcat HelloWorld

5. Java Security Configurations

Generate a Java Keystore (JKS) file:

keytool -genkeypair -alias mykey -keyalg RSA -keystore keystore.jks -storepass password

Export a certificate from a JKS file:

keytool -exportcert -alias mykey -keystore keystore.jks -file mycert.cer

Import a certificate into a JKS file:

keytool -importcert -alias newcert -file newcert.cer -keystore keystore.jks

List entries in a JKS file:
```
keytool -list -v -keystore keystore.jks
```

Enable SSL in a Java application:

System.setProperty("javax.net.ssl.keyStore", "keystore.jks");
System.setProperty("javax.net.ssl.keyStorePassword", "password");
System.setProperty("javax.net.ssl.trustStore", "truststore.jks");
System.setProperty("javax.net.ssl.trustStorePassword", "password");

6. Java Packaging and Deployment

Create a self-contained application with jlink:

jlink --module-path $JAVA_HOME/jmods --add-modules java.base,java.logging --output myapp

Create a native image with GraalVM:
```
native-image -jar myapp.jar
```

Deploy a Java application using Docker:

FROM openjdk:11-jre-slim
COPY target/myapp.jar /app/myapp.jar
ENTRYPOINT ["java", "-jar", "/app/myapp.jar"]

docker build -t myapp .
docker run -p 8080:8080 myapp

Deploy a Java application using Kubernetes:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:latest
        ports:
        - containerPort: 8080

kubectl apply -f deployment.yaml

7. Java Code Quality Tools

Checkstyle:

checkstyle -c /google_checks.xml HelloWorld.java

PMD:

pmd -d src -R rulesets/java/basic.xml -f text

FindBugs:
```
findbugs -textui -effort:max -low src
```
SonarQube:
```
sonar-scanner
```
SpotBugs:
```
spotbugs -textui -effort:max -low src
```

8. Java Documentation and Annotation Processing

Generate Javadoc with custom tags:

javadoc -d doc -tag custom:a:"Custom Tag" HelloWorld.java

Create a custom annotation processor:

@SupportedAnnotationTypes("com.example.CustomAnnotation")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class CustomProcessor extends AbstractProcessor {
    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        for (Element element : roundEnv.getElementsAnnotatedWith(CustomAnnotation.class)) {
            processingEnv.getMessager().printMessage(Diagnostic.Kind.NOTE, "Processing: " + element.toString());
        }
        return true;
    }
}

Use annotation processing in a Maven project:

<build>
  <plugins>
    <plugin>
      <groupId>org.bsc.maven</groupId>
      <artifactId>maven-processor-plugin</artifactId>
      <version>3.3.3</version>
      <executions>
        <execution>
          <id>process</id>
          <goals>
            <goal>process</goal>
          </goals>
        </execution>
      </executions>
      <configuration>
        <processors>
          <processor>com.example.CustomProcessor</processor>
        </processors>
      </configuration>
    </plugin>
  </plugins>
</build>

This comprehensive list of Java CLI commands and techniques covers everything from basic operations to advanced configurations and techniques. This should be a valuable reference for both everyday development tasks and more specialized operations.

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Java

Java CLI Commands

1. Java Version Management

2. Java Compilation and Execution

3. Java Package Management

4. Java Environment Management

5. Java Build Tools

6. Java Testing

7. Java Profiling and Debugging

8. Java Documentation

Advanced Java Techniques

1. Advanced JVM Options

2. Advanced Build Configurations

3. Advanced Testing Techniques

4. Java Performance Tuning

5. Java Security Configurations

6. Java Packaging and Deployment

7. Java Code Quality Tools

8. Java Documentation and Annotation Processing

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Java

Java CLI Commands

1. Java Version Management

2. Java Compilation and Execution

3. Java Package Management

4. Java Environment Management

5. Java Build Tools

6. Java Testing

7. Java Profiling and Debugging

8. Java Documentation

Advanced Java Techniques

1. Advanced JVM Options

2. Advanced Build Configurations

3. Advanced Testing Techniques

4. Java Performance Tuning

5. Java Security Configurations

6. Java Packaging and Deployment

7. Java Code Quality Tools

8. Java Documentation and Annotation Processing

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