关于Java Stream 的例子（书名：Java9编程参考官方大全第29章的第一个例子）

本文通过实例演示了如何使用 Java 的 Stream API 来处理集合数据，包括获取最大最小值、排序、过滤等操作。

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import java.util.*;
import java.util.stream.*;

public class StreamDemo {
   public static void main(String[] args){
       ArrayList<Integer> myList=new ArrayList<>();
       myList.add(7);
       myList.add(18);
       myList.add(10);
       myList.add(24);
       myList.add(17);
       myList.add(5);
       System.out.println("Original list："+myList);
       //Obtain a Stream to the array list.
       Stream<Integer> myStream=myList.stream();
       //obtain the max and min value by use of min(),max(),isPresent(),and get().
       Optional<Integer> minVal=myStream.min(Integer::compare);
       if(minVal.isPresent()) System.out.println("Minimum value: "+minVal.get());
       //must obtain a new stream because min() is a terminal operation that consumed the stream.
       //Stream<Integer>
       //myStream=myList.stream();
       Stream<Integer>    myStream2=myList.stream();
       //obtain the max and min value by use of min(),max(),isPresent(),and get().
       Optional<Integer> maxVal=myStream2.max(Integer::compare);
       if(maxVal.isPresent()) System.out.println("Maximum value: "+maxVal.get());
       //sort the stream by use of sorted().
       Stream<Integer> sortedStream=myList.stream().sorted();
       //Display the sorted stream by use foreach().
       System.out.println("Sorted stream: ");
       sortedStream.forEach((n)->System.out.print(n+" "));
       System.out.println();
       //Display only the odd value by use of filter().
       Stream<Integer> oddVals=myList.stream().sorted().filter((n)->(n%2)==1);
       System.out.println("Odd values: ");
       oddVals.forEach((n)->System.out.print(n+" "));
       System.out.println();
       //Display only the odd values that are greater than 5,Notice that two filter operations are pipelined.
       oddVals=myList.stream().filter((n)->(n%2)==1).filter((n)->n>5);
       System.out.println("Odd values greater than 5 : ");
       oddVals.forEach((n)->System.out.print(n+" "));
       System.out.println();

   }

}
执行结果:

Original list：[7, 18, 10, 24, 17, 5]
Minimum value: 5
Maximum value: 24
Sorted stream:
5 7 10 17 18 24
Odd values:
5 7 17
Odd values greater than 5 :
7 17