ゴール

"【Hello world】"と"【Wild Stars】"を出力する

いろいろな共通化

1. 共通化しない

public class Main {
    public static void main(String[] args) {
        HelloWorld hello = new HelloWorld();
        hello.greet();
        WildStars ws = new WildStars();
        ws.greet();
    }
}


public class HelloWorld {
    public void greet() {
        System.out.println("【Hello world】");
    }
}


public class WildStars {
    public void greet() {
        System.out.println("【Wild Stars】");
    }
}

2. 継承

public class Main {
    public static void main(String[] args) {
        HelloWorld hello = new HelloWorld();
        hello.greet();
        WildStars ws = new WildStars();
        ws.greet();
    }
}

public class BaseGreet {
	public String message;

	public void greet() {
		System.out.println("【" + message + "】");
	}
}

public class HelloWorld extends BaseGreet {
	public HelloWorld() {
		this.message = "Hello world";
	}
}

public class WildStars extends BaseGreet {
	public WildStars() {
		this.message = "Wild Stars";
	}
}

3. インタフェース

public class Main {
    public static void main(String[] args) {
        IGreet hello = new HelloWorld();
        hello.greet();
        IGreet ws = new WildStars();
        ws.greet();
    }
}

public interface IGreet {

	void greet();

}

public class HelloWorld implements IGreet {
	@Override
	public void greet() {
		System.out.println("【Hello world】");
	}
}

public class WildStars implements IGreet{
	@Override
	public void greet() {
		System.out.println("【Wild Stars】");
	}
}

4. ユーティリティー関数

public class Main {
    public static void main(String[] args) {
        GreetUtility.greet("Hello world");
        GreetUtility.greet("Wild Stars");
    }
}

public final class GreetUtility {
	public static void greet(String message) {
		System.out.println("【" + message + "】");
	}
}

5. 委譲

public class Main {
    public static void main(String[] args) {
        HelloWorld hello = new HelloWorld();
        hello.greet();
        WildStars ws = new WildStars();
        ws.greet();
    }
}

public final class GreetUtility {
	public static void greet(String message) {
		System.out.println("【" + message + "】");
	}
}

public class HelloWorld {
    public void greet() {
        GreetUtility.greet("Hello world");
    }
}

public class WildStars {
    public void greet() {
    	GreetUtility.greet("Wild stars");
    }
}

6. 関数生成

import java.util.function.Consumer;

public class Main {
    public static void main(String[] args) {
    	Consumer<String> greet = new Consumer<String>() {
			@Override
			public void accept(String message) {
				System.out.println("【" + message + "】");
			}
		};
    	greet.accept("Hello world");
    	greet.accept("Wild Stars");
    }
}