Java OptionalDouble getAsDouble()用法及代碼示例

OptionalDouble幫助我們創建一個可能包含也可能不包含double值的對象。 getAsDouble()方法返回值如果OptionalDouble對象中存在一個值，否則拋出NoSuchElementException。

用法:

public double getAsDouble()

參數：此方法不接受任何內容。

返回值：此方法返回此OptionalDouble描述的值。

異常：如果不存在任何值，則此方法將引發NoSuchElementException

以下示例程序旨在說明getAsDouble()方法：

示例1:

// Java program to demonstrate 
// OptionalDouble.getAsDouble() method 
  
import java.util.OptionalDouble; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // Create an OptionalDouble instance 
        OptionalDouble opDouble 
            = OptionalDouble.of(44356.455); 
  
        System.out.println("OptionalDouble: "
                           + opDouble.toString()); 
  
        // Get value in this instance 
        // using getAsDouble() 
        System.out.println("Value in OptionalDouble = "
                           + opDouble.getAsDouble()); 
    } 
}

輸出：

OptionalDouble: OptionalDouble[44356.455]
Value in OptionalDouble = 44356.455

示例2:

// Java program to demonstrate 
// OptionalDouble.getAsDouble() method 
  
import java.util.OptionalDouble; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        try { 
  
            // Create an OptionalDouble instance 
            OptionalDouble opDouble = OptionalDouble.empty(); 
  
            System.out.println("OptionalDouble: "
                               + opDouble.toString()); 
  
            // Get value in this instance 
            // using getAsDouble() 
            System.out.println("Value in OptionalDouble = "
                               + opDouble.getAsDouble()); 
        } 
        catch (Exception e) { 
  
            System.out.println("Exception: " + e); 
        } 
    } 
}

輸出：

OptionalDouble: OptionalDouble.empty
Exception: java.util.NoSuchElementException: No value present

參考文獻： https://docs.oracle.com/javase/10/docs/api/java/util/OptionalDouble.html#getAsDouble()

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