Get SharePoint List Items using SharePoint Framework React

I am getting SharePoint list items using framework react with following code:

Developing SharePoint Framework Web Parts Using ReactJS

import * as React from 'react';  
import { css } from 'office-ui-fabric-react';  
import styles from './Splistitems.module.scss';  
import { ISplistitemsProps } from './ISplistitemsProps';  
import * as jquery from 'jquery';   

export interface ISplistitemsState{  
  items:[  
        {  
          "Title":string           
        }]  
}  


export default class Splistitems extends React.Component<ISplistitemsProps, void> {
    public constructor(props: ISplistitemsProps, state: ISplistitemsState){  
        super(props);  
        this.state = {  // This `this.state` throws error
          items: [  
            {  
              "Title": ""           
            }  
          ]  
        };  
      } 

public componentWillMount(){ 
//..
//..
}
public render(): React.ReactElement<IUpcomingEventsProps> {
//..
//..
}
}

Here, line this.state throws following error:

Type '{ items: { "Title": string; }[]; }' is not assignable to type 'void'.

what is the problem ??