What is command design pattern explain with a java example
user
the command design pattern is a behavioral design pattern that turns a request into a stand-alone object that contains all information about the request. this allows decoupling the sender of a request from the object that performs the request. the pattern is particularly useful when you need to queue tasks, support undo/redo, and add features easily.

here's a java example to illustrate the command design pattern:

1. create command interface:

```java
public interface command {
    void execute();
}
```

2. create concrete commands:

```java
public class turnoncommand implements command {
    light light;

    public turnoncommand(light light) {
        this.light = light;
    }

    public void execute() {
        light.turnon();
    }
}

public class turnoffcommand implements command {
    light light;

    public turnoffcommand(light light) {
        this.light = light;
    }

    public void execute() {
        light.turnoff();
    }
}
```

3. create receiver:

```java
public class light {
    public void turnon() {
        system.out.println("light is on.");
    }

    public void turnoff() {
        system.out.println("light is off.");
    }
}
```

4. create invoker:

```java
public class remotecontrol {
    command command;

    public void setcommand(command command) {
        this.command = command;
    }

    public void pressbutton() {
        command.execute();
    }
}
```

5. client:

```java
public class client {
    public static void main(string[] args) {
        // create receiver
        light light = new light();

        // create commands
        turnoncommand turnoncommand = new turnoncommand(light);
        turnoffcommand turnoffcommand = new turnoffcommand(light);

        // set up invoker with different commands
        remotecontrol remotecontrol = new remotecontrol();

        // execute turn on command
        remotecontrol.setcommand(turnoncommand);
        remotecontrol.pressbutton(); // output: light is on.

        // execute turn off command
        remotecontrol.setcommand(turnoffcommand);
        remotecontrol.pressbutton(); // output: light is off.
    }
}
```

in this example, we have a `light` class (receiver), which can be turned on and off. we then create the `turnoncommand` and `turnoffcommand` (concrete commands) which implement the `command` interface. these commands encapsulate the request with the required receiver. the `remotecontrol` class (invoker) is responsible for executing the commands. and the client configures the invoker with specific commands and triggers the actions.
assistant
The Command Design Pattern is a behavioral design pattern that turns a request into a stand-alone object that contains all information about the request. This allows decoupling the sender of a request from the object that performs the request. The pattern is particularly useful when you need to queue tasks, support undo/redo, and add features easily.

Here's a Java example to illustrate the Command Design Pattern:

1. Create Command Interface:

```java
public interface Command {
    void execute();
}
```

2. Create Concrete Commands:

```java
public class TurnOnCommand implements Command {
    Light light;

    public TurnOnCommand(Light light) {
        this.light = light;
    }

    public void execute() {
        light.turnOn();
    }
}

public class TurnOffCommand implements Command {
    Light light;

    public TurnOffCommand(Light light) {
        this.light = light;
    }

    public void execute() {
        light.turnOff();
    }
}
```

3. Create Receiver:

```java
public class Light {
    public void turnOn() {
        System.out.println("Light is on.");
    }

    public void turnOff() {
        System.out.println("Light is off.");
    }
}
```

4. Create Invoker:

```java
public class RemoteControl {
    Command command;

    public void setCommand(Command command) {
        this.command = command;
    }

    public void pressButton() {
        command.execute();
    }
}
```

5. Client:

```java
public class Client {
    public static void main(String[] args) {
        // Create receiver
        Light light = new Light();

        // Create commands
        TurnOnCommand turnOnCommand = new TurnOnCommand(light);
        TurnOffCommand turnOffCommand = new TurnOffCommand(light);

        // Set up invoker with different commands
        RemoteControl remoteControl = new RemoteControl();

        // Execute turn on command
        remoteControl.setCommand(turnOnCommand);
        remoteControl.pressButton(); // Output: Light is on.

        // Execute turn off command
        remoteControl.setCommand(turnOffCommand);
        remoteControl.pressButton(); // Output: Light is off.
    }
}
```

In this example, we have a `Light` class (Receiver), which can be turned on and off. We then create the `TurnOnCommand` and `TurnOffCommand` (Concrete Commands) which implement the `Command` interface. These commands encapsulate the request with the required receiver. The `RemoteControl` class (Invoker) is responsible for executing the commands. And the client configures the invoker with specific commands and triggers the actions.
assistant