[JAVA-14174] Renamed paterns to paterns-module (#12718)

* [JAVA-14174] Renamed paterns to paterns-module

* [JAVA-14174] naming fixes

Co-authored-by: panagiotiskakos <[email protected]>

patterns-modules/design-patterns-behavioral/README.md

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+### Relevant Articles:
+- [The Observer Pattern in Java](https://www.baeldung.com/java-observer-pattern)
+- [Visitor Design Pattern in Java](https://www.baeldung.com/java-visitor-pattern)
+- [Interpreter Design Pattern in Java](https://www.baeldung.com/java-interpreter-pattern)
+- [State Design Pattern in Java](https://www.baeldung.com/java-state-design-pattern)
+- [Implementing the Template Method Pattern in Java](https://www.baeldung.com/java-template-method-pattern)
+- [Chain of Responsibility Design Pattern in Java](https://www.baeldung.com/chain-of-responsibility-pattern)
+- [The Command Pattern in Java](https://www.baeldung.com/java-command-pattern)
+- [The Mediator Pattern in Java](https://www.baeldung.com/java-mediator-pattern)
+- [Introduction to the Null Object Pattern](https://www.baeldung.com/java-null-object-pattern)
+- [Avoid Check for Null Statement in Java](https://www.baeldung.com/java-avoid-null-check)

patterns-modules/design-patterns-behavioral/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>design-patterns-behavioral</artifactId>
+    <version>1.0</version>
+    <name>design-patterns-behavioral</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>patterns-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations</artifactId>
+            <version>${intellij.annotations.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.code.findbugs</groupId>
+            <artifactId>annotations</artifactId>
+            <version>${findbugs.annotations.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <intellij.annotations.version>16.0.2</intellij.annotations.version>
+        <findbugs.annotations.version>3.0.1</findbugs.annotations.version>
+    </properties>
+
+</project>

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/AuthenticationProcessor.java

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+package com.baeldung.chainofresponsibility;
+
+public abstract class AuthenticationProcessor {
+
+    // next element in chain or responsibility
+    public AuthenticationProcessor nextProcessor;
+    
+    public AuthenticationProcessor(AuthenticationProcessor nextProcessor) {
+        this.nextProcessor = nextProcessor;
+    }
+
+    public abstract boolean isAuthorized(AuthenticationProvider authProvider);
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/AuthenticationProvider.java

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+package com.baeldung.chainofresponsibility;
+
+public interface AuthenticationProvider {
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/OAuthAuthenticationProcessor.java

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+package com.baeldung.chainofresponsibility;
+
+public class OAuthAuthenticationProcessor extends AuthenticationProcessor {
+
+    public OAuthAuthenticationProcessor(AuthenticationProcessor nextProcessor) {
+        super(nextProcessor);
+    }
+
+    @Override
+    public boolean isAuthorized(AuthenticationProvider authProvider) {
+
+        if (authProvider instanceof OAuthTokenProvider) {
+            return Boolean.TRUE;
+        } else if (nextProcessor != null) {
+            return nextProcessor.isAuthorized(authProvider);
+        } else {
+            return Boolean.FALSE;
+        }
+    }
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/OAuthTokenProvider.java

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+package com.baeldung.chainofresponsibility;
+
+public class OAuthTokenProvider implements AuthenticationProvider {
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/SamlAuthenticationProvider.java

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+package com.baeldung.chainofresponsibility;
+
+public class SamlAuthenticationProvider implements AuthenticationProvider {
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/UsernamePasswordAuthenticationProcessor.java

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+package com.baeldung.chainofresponsibility;
+
+public class UsernamePasswordAuthenticationProcessor extends AuthenticationProcessor {
+
+    public UsernamePasswordAuthenticationProcessor(AuthenticationProcessor nextProcessor) {
+        super(nextProcessor);
+    }
+
+    @Override
+    public boolean isAuthorized(AuthenticationProvider authProvider) {
+        if (authProvider instanceof UsernamePasswordProvider) {
+            return Boolean.TRUE;
+        } else if (nextProcessor != null) {
+            return nextProcessor.isAuthorized(authProvider);
+        } else {
+            return Boolean.FALSE;
+        }
+    }
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/chainofresponsibility/UsernamePasswordProvider.java

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+package com.baeldung.chainofresponsibility;
+
+public class UsernamePasswordProvider implements AuthenticationProvider {
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/command/client/TextFileApplication.java

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+package com.baeldung.command.client;
+
+import com.baeldung.command.command.OpenTextFileOperation;
+import com.baeldung.command.command.SaveTextFileOperation;
+import com.baeldung.command.command.TextFileOperation;
+import com.baeldung.command.invoker.TextFileOperationExecutor;
+import com.baeldung.command.receiver.TextFile;
+
+public class TextFileApplication {
+    
+    public static void main(String[] args) {
+        
+        TextFileOperation openTextFileOperation = new OpenTextFileOperation(new TextFile("file1.txt"));
+        TextFileOperation saveTextFileOperation = new SaveTextFileOperation(new TextFile("file2.txt"));
+        TextFileOperationExecutor textFileOperationExecutor = new TextFileOperationExecutor();
+        System.out.println(textFileOperationExecutor.executeOperation(openTextFileOperation));
+        System.out.println(textFileOperationExecutor.executeOperation(saveTextFileOperation));
+    }   
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/command/command/OpenTextFileOperation.java

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+package com.baeldung.command.command;
+
+import com.baeldung.command.receiver.TextFile;
+
+public class OpenTextFileOperation implements TextFileOperation {
+
+    private final TextFile textFile;
+    
+    public OpenTextFileOperation(TextFile textFile) {
+        this.textFile = textFile;
+    }
+    
+    @Override
+    public String execute() {
+        return textFile.open();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/command/command/SaveTextFileOperation.java

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+package com.baeldung.command.command;
+
+import com.baeldung.command.receiver.TextFile;
+
+public class SaveTextFileOperation implements TextFileOperation {
+    
+    private final TextFile textFile;
+    
+    public SaveTextFileOperation(TextFile textFile) {
+        this.textFile = textFile;
+    }
+    
+    @Override
+    public String execute() {
+        return textFile.save();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/command/command/TextFileOperation.java

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+package com.baeldung.command.command;
+
+@FunctionalInterface
+public interface TextFileOperation {
+    
+    String execute();
+    
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/command/invoker/TextFileOperationExecutor.java

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+package com.baeldung.command.invoker;
+
+import com.baeldung.command.command.TextFileOperation;
+import java.util.ArrayList;
+import java.util.List;
+
+public class TextFileOperationExecutor {
+    
+    private final List<TextFileOperation> textFileOperations = new ArrayList<>();
+    
+    public String executeOperation(TextFileOperation textFileOperation) {
+        textFileOperations.add(textFileOperation);
+        return textFileOperation.execute();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/command/receiver/TextFile.java

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+package com.baeldung.command.receiver;
+
+public class TextFile {
+    
+    private final String name;
+    
+    public TextFile(String name) {
+        this.name = name;
+    }
+    
+    public String open() {
+        return "Opening file " + name;
+    }
+    
+    public String read() {  
+        return "Reading file " + name;
+    }
+    
+    public String write() {  
+        return "Writing to file " + name;
+    }
+    
+    public String save() {  
+        return "Saving file " + name;
+    }
+    
+    public String copy() {  
+        return "Copying file " + name;
+    }
+    
+    public String paste() {  
+        return "Pasting file " + name;
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/Context.java

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+package com.baeldung.interpreter;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+class Context {
+
+    private static Map<String, List<Row>> tables = new HashMap<>();
+
+    static {
+        List<Row> list = new ArrayList<>();
+        list.add(new Row("John", "Doe"));
+        list.add(new Row("Jan", "Kowalski"));
+        list.add(new Row("Dominic", "Doom"));
+
+        tables.put("people", list);
+    }
+
+    private String table;
+    private String column;
+
+    /**
+     * Index of column to be shown in result.
+     * Calculated in {@link #setColumnMapper()}
+     */
+    private int colIndex = -1;
+
+    /**
+     * Default setup, used for clearing the context for next queries.
+     * See {@link Context#clear()}
+     */
+    private static final Predicate<String> matchAnyString = s -> s.length() > 0;
+    private static final Function<String, Stream<? extends String>> matchAllColumns = Stream::of;
+    /**
+     * Varies based on setup in subclasses of {@link Expression}
+     */
+    private Predicate<String> whereFilter = matchAnyString;
+    private Function<String, Stream<? extends String>> columnMapper = matchAllColumns;
+
+    void setColumn(String column) {
+        this.column = column;
+        setColumnMapper();
+    }
+
+    void setTable(String table) {
+        this.table = table;
+    }
+
+    void setFilter(Predicate<String> filter) {
+        whereFilter = filter;
+    }
+
+    /**
+     * Clears the context to defaults.
+     * No filters, match all columns.
+     */
+    void clear() {
+        column = "";
+        columnMapper = matchAllColumns;
+        whereFilter = matchAnyString;
+    }
+
+    List<String> search() {
+
+        List<String> result = tables.entrySet()
+                .stream()
+                .filter(entry -> entry.getKey().equalsIgnoreCase(table))
+                .flatMap(entry -> Stream.of(entry.getValue()))
+                .flatMap(Collection::stream)
+                .map(Row::toString)
+                .flatMap(columnMapper)
+                .filter(whereFilter)
+                .collect(Collectors.toList());
+
+        clear();
+
+        return result;
+    }
+
+    /**
+     * Sets column mapper based on {@link #column} attribute.
+     * Note: If column is unknown, will remain to look for all columns.
+     */
+    private void setColumnMapper() {
+        switch (column) {
+            case "*":
+                colIndex = -1;
+                break;
+            case "name":
+                colIndex = 0;
+                break;
+            case "surname":
+                colIndex = 1;
+                break;
+        }
+        if (colIndex != -1) {
+            columnMapper = s -> Stream.of(s.split(" ")[colIndex]);
+        }
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/Expression.java

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+package com.baeldung.interpreter;
+
+import java.util.List;
+
+interface Expression {
+    List<String> interpret(Context ctx);
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/From.java

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+package com.baeldung.interpreter;
+
+import java.util.List;
+
+class From implements Expression {
+
+    private String table;
+    private Where where;
+
+    From(String table) {
+        this.table = table;
+    }
+
+    From(String table, Where where) {
+        this.table = table;
+        this.where = where;
+    }
+
+    @Override
+    public List<String> interpret(Context ctx) {
+        ctx.setTable(table);
+        if (where == null) {
+            return ctx.search();
+        }
+        return where.interpret(ctx);
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/InterpreterDemo.java

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+package com.baeldung.interpreter;
+
+import java.util.List;
+
+
+public class InterpreterDemo {
+
+    public static void main(String[] args) {
+
+        Expression query = new Select("name", new From("people"));
+        Context ctx = new Context();
+        List<String> result = query.interpret(ctx);
+        System.out.println(result);
+
+        Expression query2 = new Select("*", new From("people"));
+        List<String> result2 = query2.interpret(ctx);
+        System.out.println(result2);
+
+        Expression query3 = new Select("name", new From("people", new Where(name -> name.toLowerCase().startsWith("d"))));
+        List<String> result3 = query3.interpret(ctx);
+        System.out.println(result3);
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/Row.java

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+package com.baeldung.interpreter;
+
+class Row {
+
+    private String name;
+    private String surname;
+
+    Row(String name, String surname) {
+        this.name = name;
+        this.surname = surname;
+    }
+
+    @Override
+    public String toString() {
+        return name + " " + surname;
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/Select.java

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+package com.baeldung.interpreter;
+
+import java.util.List;
+
+class Select implements Expression {
+
+    private String column;
+    private From from;
+
+    Select(String column, From from) {
+        this.column = column;
+        this.from = from;
+    }
+
+    @Override
+    public List<String> interpret(Context ctx) {
+        ctx.setColumn(column);
+        return from.interpret(ctx);
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/interpreter/Where.java

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+package com.baeldung.interpreter;
+
+import java.util.List;
+import java.util.function.Predicate;
+
+class Where implements Expression {
+
+    private Predicate<String> filter;
+
+    Where(Predicate<String> filter) {
+        this.filter = filter;
+    }
+
+    @Override
+    public List<String> interpret(Context ctx) {
+        ctx.setFilter(filter);
+        return ctx.search();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/mediator/Button.java

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+package com.baeldung.mediator;
+
+public class Button {
+    private Mediator mediator;
+
+    public void setMediator(Mediator mediator) {
+        this.mediator = mediator;
+    }
+
+    public void press() {
+        this.mediator.press();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/mediator/Fan.java

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+package com.baeldung.mediator;
+
+public class Fan {
+    private Mediator mediator;
+    private boolean isOn = false;
+
+    public void setMediator(Mediator mediator) {
+        this.mediator = mediator;
+    }
+
+    public boolean isOn() {
+        return isOn;
+    }
+
+    public void turnOn() {
+        this.mediator.start();
+        isOn = true;
+    }
+
+    public void turnOff() {
+        isOn = false;
+        this.mediator.stop();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/mediator/Mediator.java

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+package com.baeldung.mediator;
+
+public class Mediator {
+    private Button button;
+    private Fan fan;
+    private PowerSupplier powerSupplier;
+
+    public void setButton(Button button) {
+        this.button = button;
+        this.button.setMediator(this);
+    }
+
+    public void setFan(Fan fan) {
+        this.fan = fan;
+        this.fan.setMediator(this);
+    }
+
+    public void setPowerSupplier(PowerSupplier powerSupplier) {
+        this.powerSupplier = powerSupplier;
+    }
+
+    public void press() {
+        if (fan.isOn()) {
+            fan.turnOff();
+        } else {
+            fan.turnOn();
+        }
+    }
+
+    public void start() {
+        powerSupplier.turnOn();
+    }
+
+    public void stop() {
+        powerSupplier.turnOff();
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/mediator/PowerSupplier.java

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+package com.baeldung.mediator;
+
+public class PowerSupplier {
+    public void turnOn() {
+        // implementation
+    }
+
+    public void turnOff() {
+        // implementation
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/nullobject/JmsRouter.java

@@ -0,0 +1,10 @@
+package com.baeldung.nullobject;
+
+public class JmsRouter implements Router {
+
+    @Override
+    public void route(Message msg) {
+        System.out.println("Routing to a JMS queue. Msg: " + msg);
+    }
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/nullobject/Message.java

@@ -0,0 +1,24 @@
+package com.baeldung.nullobject;
+
+public class Message {
+
+    private String body;
+
+    private String priority;
+
+    public Message(String body, String priority) {
+        this.body = body;
+        this.priority = priority;
+    }
+
+    public String getPriority() {
+        return priority;
+    }
+
+    @Override
+    public String toString() {
+        return "{body='" + body + '\'' +
+                ", priority='" + priority + '\'' +
+                '}';
+    }
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/nullobject/NullRouter.java

@@ -0,0 +1,10 @@
+package com.baeldung.nullobject;
+
+public class NullRouter implements Router {
+
+    @Override
+    public void route(Message msg) {
+        // do nothing
+    }
+
+}

patterns-modules/design-patterns-behavioral/src/main/java/com/baeldung/nullobject/Router.java

@@ -0,0 +1,7 @@
+package com.baeldung.nullobject;
+
+public interface Router {
+
+    void route(Message msg);
+
+}