如何在Java流API中从Stream <tuple2 <k，v =“” >>中执行Map <k，v =“”>？

Question

哦。我有Java 8，想收集

class Celebration extends React.Component {


constructor(props){
    super(props);
    this.printProps = this.printProps.bind(this);
  }
  printProps(){
    this.props.reset();
  }
  render(){
    return (
     <div className="alert alert-success alert-dismissible">
    <a href="#" className="close" data-dismiss="alert" aria-label="close" onClick={this.printProps.bind()}>&times;</a>
    <strong>Game Over!</strong> Player {this.props.winner} won!
  </div>
    );
  }
}
class Square extends React.Component {
 constructor(props) {
   super(props);
   this.state = {
     value: null,
     selected: this.props.selected
   };
 }
 toggleState(){
   if(this.state.value==null)
       {
         this.setState({value: this.props.value});
         this.props.selected(this.props.number);
         this.props.forToggle();
       }
     }
 render() {
   return (
     <button
       className="square"
       onClick={() => this.toggleState()}
     >
       {this.state.value}
     </button>
   );
 }
}

class Board extends React.Component {
 renderSquare(i, val) {
   return <Square value={i} number={val} forToggle={this.props.forToggle} selected={this.props.selected}/>;
 }

 render() {
   const status = 'Next player: '+this.props.playerTurn;

   return (
     <div>
       <div className="status">{status}</div>
       <div className="board-row">
         {this.renderSquare(this.props.playerTurn,1)}
         {this.renderSquare(this.props.playerTurn,2)}
         {this.renderSquare(this.props.playerTurn,3)}
       </div>
       <div className="board-row">
         {this.renderSquare(this.props.playerTurn,4)}
         {this.renderSquare(this.props.playerTurn,5)}
         {this.renderSquare(this.props.playerTurn,6)}
       </div>
       <div className="board-row">
         {this.renderSquare(this.props.playerTurn,7)}
         {this.renderSquare(this.props.playerTurn,8)}
         {this.renderSquare(this.props.playerTurn,9)}
       </div>
     </div>
   );
 }
}

class Game extends React.Component {
 constructor(props){
   super(props);
   this.state = this.initialState;
 }
 get initialState() {
      return {
          playerTurn: null,
          selectedX: new Set(),
          selectedO: new Set(),
          winnerDecided: false
      };
 }
 masterReset(){
   this.setState({
     winnerDecided: false
   });
 }
 addInSelected(i){
   let currentSet;
   if(this.state.playerTurn == 'X')
      currentSet=this.state.selectedX;
   else
      currentSet=this.state.selectedO;
   currentSet.add(i);
   if(currentSet.has(1) && currentSet.has(2) && currentSet.has(3))
     this.setState({winnerDecided: true});
   else if(currentSet.has(4) && currentSet.has(5) && currentSet.has(6))
     this.setState({winnerDecided: true});
   else if(currentSet.has(7) && currentSet.has(8) && currentSet.has(9))
     this.setState({winnerDecided: true});
   else if(currentSet.has(1) && currentSet.has(4) && currentSet.has(7))
     this.setState({winnerDecided: true});
   else if(currentSet.has(2) && currentSet.has(5) && currentSet.has(8))
     this.setState({winnerDecided: true});
   else if(currentSet.has(3) && currentSet.has(6) && currentSet.has(9))
     this.setState({winnerDecided: true});
   else if(currentSet.has(1) && currentSet.has(5) && currentSet.has(9))
     this.setState({winnerDecided: true});
   else if(currentSet.has(3) && currentSet.has(5) && currentSet.has(7))
     this.setState({winnerDecided: true});
 }
 togglePlayer(){
   if(this.state.playerTurn.localeCompare('X')==0)
     this.setState({playerTurn: 'O'});
   else
     this.setState({playerTurn: 'X'});
 }
 decideWinner(){
   if(this.state.playerTurn == 'X')
     return 'O';
   else
     return 'X';
 }
 componentDidMount(){
   this.setState({playerTurn: 'X'});
   //alert("game mounted");
 }
 render() {
   if(!this.state.winnerDecided)
   return (
     <div className="game">
       <div className="game-board">
         <Board playerTurn={this.state.playerTurn} selected={this.addInSelected.bind(this)} forToggle={this.togglePlayer.bind(this)}/>
       </div>
       <div className="game-info">
         <div>{/* status */}</div>
         <ol>{/* TODO */}</ol>
       </div>
     </div>
   );

   else
     return (<div>
         <Celebration winner={this.decideWinner()} reset={this.masterReset.bind(this)} />
         </div>);
 }
}

// ========================================

ReactDOM.render(
 <Game />,
 document.getElementById('root')
);

来自

Map<K, V> 

由于冗长的语法，我不想使用Pair。有什么办法

Stream<Tuple2<K, V>>

感谢

Answer 1

AFAIK ，这在Java中是无法避免的（与在scala中完成的方式相比。）

但是，如果您打算在代码中使用大量的元组到映射转换，并且希望避免冗长的语法，则可以创建自定义TupleCollector并添加toMap方法。

这可能是您进入scala的壁橱。

static class TupleCollector {
        public static <K, V, T extends Tuple2<K, V>> Collector<T, ?, Map<K, V>> toMap() {
            return Collectors.toMap(T::_1, T::_2);
        }
    }

调用代码

import static TupleCollector.toMap
...
myStream.collect(toMap());

PS： 再说一次，如果不通过代码审查阶段，我也不会感到惊讶。