React JS - State with class component

App.js - 

import './App.css';

import React, {useState, Component} from 'react';

class App extends Component{

  constructor(){

    super();

    this.state={data:"Krishan"}

  }

  fun2(){

    this.setState({data:"Dev"})

  }

  render(){

    return(

      <div>

        <h1>{this.state.data}</h1>

        <button onClick={()=>this.fun2()}>Click Me</button>

      </div>

    )

  }

}

export default App;