> For the complete documentation index, see [llms.txt](https://heunnajo.gitbook.io/java/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://heunnajo.gitbook.io/java/single-inheritance-object-class.md).

# Single Inheritance, Object Class

Java allows only single inheritance.

```java
class TvDVD extends Tv, DVD {...}//error.
```

inherit deeper relation one and composite remains.

```java
class TvDVD extends Tv {
    DVD dvd = new DVD();
    
    void play() {dvd.play();}
    void stop() {dvd.play();}
    void rew() {dvd.play();}
    void ff() {dvd.play();}
}
```

* Object class : parent of every class

Class which has no parent inherits Object class automatically.

\=> All of class inherit methods from Object class. ex) **toString()**, equals(Object obj), hashCode(),...

toString() : return class name and address(not exactly but meaningful)

```java
//both are same result
System.out.println("c.toString");
System.out.println(c);
```