双流。Java 中的 Builder build()
原文:https://www . geesforgeks . org/double stream-builder-build-in-Java/
DoubleStream。构建器构建()构建流，将该构建器转换到构建状态。
语法:
DoubleStream build()
返回值:这个方法返回构建的流。
注意:一个流构建器有一个生命周期，从构建阶段开始，在此期间可以添加元素，然后过渡到构建阶段，之后可以不添加元素。构建阶段在调用 build()方法时开始，该方法创建一个有序流，其元素是按照添加顺序添加到流构建器中的元素。
下面是举例说明 build()方法的例子:
例 1:
// Java code to show the implementation
// of DoubleStream.Builder build()
import java.util.stream.DoubleStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating a Stream in building phase
DoubleStream.Builder b = DoubleStream.builder();
// Adding elements into the stream
b.add(1.2);
b.add(2.4);
b.add(3.87);
b.add(4.78);
// Constructing the built stream using build()
// This will enter the stream in built phase
b.build().forEach(System.out::println);
}
}
Output:
1.2
2.4
3.87
4.78
示例 2: 在调用 build()方法后尝试在中添加元素(当流处于构建阶段时)。
// Java code to show the implementation
// of DoubleStream.Builder build()
import java.util.stream.DoubleStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating a Stream in building phase
DoubleStream.Builder b = DoubleStream.builder();
// Adding elements into the stream
b.add(1.2);
b.add(2.4);
b.add(3.87);
b.add(4.78);
// Constructing the built stream using build()
// This will enter the stream in built phase
// Now no more elements can be added to this stream
b.build().forEach(System.out::println);
// Trying to add more elements in built phase
// This will cause exception
try {
b.add(50.547);
}
catch (Exception e) {
System.out.println("\nException: " + e);
}
}
}
Output:
1.2
2.4
3.87
4.78
Exception: java.lang.IllegalStateException
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