Package com.singularsys.extensions.stream

Class StreamFirst

java.lang.Object

com.singularsys.jep.functions.PostfixMathCommand

com.singularsys.jep.functions.UnaryFunction

com.singularsys.extensions.stream.StreamFirst

All Implemented Interfaces:

ZeroLengthBehaviourI, ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI, JepComponent, PostfixMathCommandI, Serializable

public class StreamFirst
extends UnaryFunction
implements JepComponent, ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

Returns the first element from a stream. Uses the Stream.findFirst() methods. By default, if the stream is empty, an exception is thrown, but the behaviour can be configured using the methods of the ZeroLengthBehaviourI interface.

See StreamFirstOr for a variant that returns the first element or a default value if the stream is empty.

See Also:

• Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class com.singularsys.jep.functions.UnaryFunction

UnaryFunction.FunctionWithException<T>

Nested classes/interfaces inherited from interface com.singularsys.jep.functions.ZeroLengthBehaviourI

ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI, ZeroLengthBehaviourI.ZeroLengthErrorBehaviour, ZeroLengthBehaviourI.ZeroLengthHelper

Field Summary

Fields inherited from class com.singularsys.jep.functions.PostfixMathCommand

curNumberOfParameters, description, name, NaN, numberOfParameters

Constructor Summary

Constructors

Constructor	Description
StreamFirst()

Method Summary

Modifier and Type	Method	Description
Object	eval(Object arg)	Evaluate the function
JepComponent	getLightWeightInstance()	Gets a light-weight instance suitable for using in multiple threads.
ZeroLengthBehaviourI	getZeroLengthHelper()	Gets the helper class which implements the zero length behaviour.
void	init(Jep jep)	Initialize the component.

Methods inherited from class com.singularsys.jep.functions.UnaryFunction

instanceOf, instanceOf, instanceOf, instanceOf, run

Methods inherited from class com.singularsys.jep.functions.PostfixMathCommand

asArray, asBool, asDouble, asInt, asLong, asStrictInt, asString, asType, checkNumberOfParameters, getDescription, getDescription, getDescriptionWithType, getName, getNumberOfParameters, setCurNumberOfParameters, setDescription, setName, toString, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.singularsys.jep.functions.ZeroLengthBehaviourI

getErrorMessage, getValueOrException, zeroLengthResultOrException

Methods inherited from interface com.singularsys.jep.functions.ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

getZeroLengthErrorBehaviour, getZeroLengthValue, setZeroLengthErrorBehaviour, setZeroLengthValue

Constructor Details

StreamFirst

public StreamFirst()

Method Details

eval

public Object eval(Object arg)
            throws EvaluationException

Description copied from class: UnaryFunction

Evaluate the function

Specified by:

eval in class UnaryFunction

Parameters:

arg - the single argument passed in

Returns:

the result of the function

Throws:

EvaluationException - on error

init

public void init(Jep jep)

Description copied from interface: JepComponent

Initialize the component. This method is called whenever a component is added to Jep. Hence, it allows components to keep track of the other components they may rely on.

Specified by:

init in interface JepComponent

Parameters:

jep - the current Jep instance

getLightWeightInstance

public JepComponent getLightWeightInstance()

Description copied from interface: JepComponent

Gets a light-weight instance suitable for using in multiple threads.

Specified by:

getLightWeightInstance in interface JepComponent

Returns:

either a new instance, null or 'this'.

getZeroLengthHelper

public ZeroLengthBehaviourI getZeroLengthHelper()

Description copied from interface: ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

Gets the helper class which implements the zero length behaviour. The standard implementation is:

ZeroLengthHelper zeroLengthHelper = new ZeroLengthHelper();
@Override
public ZeroLengthBehaviourI getZeroLengthHelper() {
    return zeroLengthHelper;
}

Specified by:

getZeroLengthHelper in interface ZeroLengthBehaviourI.DefaultZeroLengthBehaviourI

Returns:

the helper class