Java LongStream mapToDouble()用法及代碼示例

LongStream mapToDouble()返回DoubleStream，該DoubleStream包含將給定函數應用於此流的元素的結果。

注意：LongStream mapToDouble()是中間操作。這些操作總是很懶。在Stream實例上調用中間操作，並在完成處理後將中間實例作為輸出提供。
用法:

DoubleStream mapToDouble(LongToDoubleFunction mapper)

參數：

DoubleStream : 一係列原始雙值元素。這是Stream的雙重原始專業化。
mapper : 適用於每個元素的無狀態函數。

返回值：該函數返回一個DoubleStream，其中包括將給定函數應用於此流的元素的結果。

示例1:

// Java code for DoubleStream mapToDouble 
// (LongToDoubleFunction mapper) 
import java.util.*; 
import java.util.stream.LongStream; 
import java.util.stream.DoubleStream; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
        // Creating an LongStream 
        LongStream stream = LongStream.of(2L, 4L, 6L, 8L, 10L); 
  
        // Using DoubleStream mapToLong(LongToDoubleFunction mapper) 
        // to return a DoubleStream consisting of the 
        // results of applying the given function to 
        // the elements of this stream. 
        DoubleStream stream1 = stream.mapToDouble(num -> (double)num); 
  
        // Displaying the elements in stream1 
        stream1.forEach(System.out::println); 
    } 
}

輸出：

2.0
4.0
6.0
8.0
10.0

示例2:

// Java code for DoubleStream mapToDouble 
// (LongToDoubleFunction mapper) 
import java.util.*; 
import java.util.stream.LongStream; 
import java.util.stream.DoubleStream; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
        // Creating an LongStream 
        LongStream stream = LongStream.range(5L, 10L); 
  
        // Using DoubleStream mapToLong(LongToDoubleFunction mapper) 
        // to return a DoubleStream consisting of the 
        // results of applying the given function to 
        // the elements of this stream. 
        DoubleStream stream1 = stream.mapToDouble(num -> (double)num / 5); 
  
        // Displaying the elements in stream1 
        stream1.forEach(System.out::println); 
    } 
}

輸出：

1.0
1.2
1.4
1.6
1.8

示例3:

// Java code for DoubleStream mapToDouble 
// (LongToDoubleFunction mapper) 
import java.util.*; 
import java.util.stream.LongStream; 
import java.util.stream.DoubleStream; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
        // Creating an LongStream 
        LongStream stream = LongStream.range(5L, 10L); 
  
        // Using DoubleStream mapToLong(LongToDoubleFunction mapper) 
        // to return a DoubleStream consisting of the 
        // results of applying the given function to 
        // the elements of this stream. 
        DoubleStream stream1 = stream.mapToDouble(Math::cos); 
  
        // Displaying the elements in stream1 
        stream1.forEach(System.out::println); 
    } 
}

輸出：

0.28366218546322625
0.9601702866503661
0.7539022543433046
-0.14550003380861354
-0.9111302618846769

相關用法

注：本文由純淨天空篩選整理自Sahil_Bansall大神的英文原創作品 LongStream mapToDouble() in Java。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。