Java DoubleStream mapToInt()

DoubleStream mapToInt() 返回一个IntStream，该IntStream由对该流的元素应用给定函数的结果组成。

注意： DoubleStream mapToInt()是一个 中间操作。 这些操作总是懒惰的。中间操作是在一个Stream实例上调用的，在它们完成处理后，会给出一个Stream实例作为输出:
语法

IntStream mapToInt(DoubleToIntFunction mapper)

参数

IntStream : 一个原始int值元素的序列。这是对Stream的int primitive specialization。
mapper : 一个应用于每个元素的无状态函数。

返回值： 该函数返回一个IntStream，由对该流的元素应用给定函数的结果组成。

例子 1 :

// Java code for IntStream mapToInt
// (DoubleToIntFunction mapper)
import java.util.*;
import java.util.stream.IntStream;
import java.util.stream.DoubleStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // Creating a DoubleStream
        DoubleStream stream = DoubleStream.of(2.3, 4.5, 6.4,
                                              8.7, 10.4);
  
        // Using IntStream mapToInt(DoubleToIntFunction mapper)
        // to return an IntStream consisting of the
        // results of applying the given function to
        // the elements of this stream.
        IntStream stream1 = stream.mapToInt(num -> (int)num);
  
        // Displaying the elements in stream1
        stream1.forEach(System.out::println);
    }
}

输出:

例2 :

// Java code for IntStream mapToInt
// (DoubleToIntFunction mapper)
import java.util.*;
import java.util.stream.IntStream;
import java.util.stream.DoubleStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // Creating a DoubleStream
        DoubleStream stream = DoubleStream.of(2.3, 4.5, 6.4,
                                              8.7, 10.4);
  
        // Using IntStream mapToInt(DoubleToIntFunction mapper)
        // to return an IntStream consisting of the
        // results of applying the given function to
        // the elements of this stream.
        IntStream stream1 = stream.mapToInt(num -> (int)num - 10000);
  
        // Displaying the elements in stream1
        stream1.forEach(System.out::println);
    }
}

输出:

例3 :

// Java code for IntStream mapToInt
// (DoubleToIntFunction mapper)
import java.util.*;
import java.util.stream.IntStream;
import java.util.stream.DoubleStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // Creating a DoubleStream
        DoubleStream stream = DoubleStream.of(1.3, 2.4, 3.4,
                                              4.5, 5.7);
  
        // Using IntStream mapToInt(DoubleToIntFunction mapper)
        // to return an IntStream consisting of the
        // results of applying the given function to
        // the elements of this stream.
        IntStream stream1 = stream.mapToInt(num -> (int)(num * num * num));
  
        // Displaying the elements in stream1
        stream1.forEach(System.out::println);
    }
}

输出: