Class SwitchBootstraps

java.lang.Object

java.lang.runtime.SwitchBootstraps

public final class SwitchBootstraps
extends Object

Bootstrap methods for linking invokedynamic call sites that implement the selection functionality of the switch statement. The bootstraps take additional static arguments corresponding to the case labels of the switch, implicitly numbered sequentially from [0..N).

Since:

21

Method Summary

Modifier and Type	Method	Description
static CallSite	enumSwitch(MethodHandles.Lookup lookup, String invocationName, MethodType invocationType, Object... labels)	Bootstrap method for linking an invokedynamic call site that implements a switch on a target of an enum type.
static CallSite	typeSwitch(MethodHandles.Lookup lookup, String invocationName, MethodType invocationType, Object... labels)	Bootstrap method for linking an invokedynamic call site that implements a switch over a target value.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Method Details

typeSwitch

public static CallSite typeSwitch(MethodHandles.Lookup lookup,
 String invocationName,
 MethodType invocationType,
 Object... labels)

Bootstrap method for linking an invokedynamic call site that implements a switch over a target value. The static arguments labels are an array of case labels which must be non-null and of type String, Integer, Class, or EnumDesc. In addition, when preview features are enabled, Long, Float, Double, and Boolean labels are also permitted.

The type of the returned CallSite's method handle will have a return type of int. It has two parameters: the first argument will be a value of the (target) type and the second will be int (restart).

If the target is null, then the method of the call site returns -1.

If the target is not null, then the method of the call site returns the index of the first element in the labels array starting from the restart index matching one of the following conditions:

• the element is of type Class that is assignable from the target's class
• the element is of type String and equals to the target
• the element is of type Integer and == to the target after unboxing if necessary
• (Preview) the element is of type Long or Boolean and == to the target after unboxing if necessary
• (Preview) the element is of type Float or Double and equals to the target after boxing if necessary
• the element is of type EnumDesc, that describes an enum constant that is == to the target

If no element in the labels array matches the target, then the method of the call site return the length of the labels array.

The value of the restart index must be between 0 (inclusive) and the length of the labels array (inclusive), both or an IndexOutOfBoundsException is thrown.

Parameters:

lookup - the full-privilege lookup context of the caller

invocationName - unused, null is permitted

invocationType - The invocation type of the CallSite with two parameters, a target type, an int, and int as a return type.

labels - case labels as described above

Returns:

a CallSite returning the first matching element as described above

Throws:

IllegalArgumentException - if any element in the labels array is null

IllegalArgumentException - if the invocation type is not a method type of first parameter of a target type, second parameter of type int and with int as its return type

IllegalArgumentException - if labels contains an element that is not of type String, Integer, Long, Float, Double, Boolean, Class or EnumDesc

IllegalArgumentException - if preview features are disabled and if labels contains an element that is of type Long, Float, Double, or Boolean

See Java Virtual Machine Specification:

4.4.6 The CONSTANT_NameAndType_info Structure
4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures

enumSwitch

public static CallSite enumSwitch(MethodHandles.Lookup lookup,
 String invocationName,
 MethodType invocationType,
 Object... labels)

Bootstrap method for linking an invokedynamic call site that implements a switch on a target of an enum type. The static arguments are used to encode the case labels associated to the switch construct, where each label can be encoded in two ways:

• as a String value, which represents the name of the enum constant associated with the label
• as a Class value, which represents the enum type associated with a type test pattern

The returned CallSite's method handle will have a return type of int and accepts two parameters: the first argument will be an Enum instance (target) and the second will be int (restart).

If the target is null, then the method of the call site returns -1.

If the target is not null, then the method of the call site returns the index of the first element in the labels array starting from the restart index matching one of the following conditions:

• the element is of type Class that is assignable from the target's class; or
• the element is of type String and equals to the target enum constant's Enum.name().

If for a given target there is no element in the labels fulfilling one of the above conditions, then the method of the call site returns the length of the labels array.

The value of the restart index must be between 0 (inclusive) and the length of the labels array (inclusive), or an IndexOutOfBoundsException is thrown.

API Note:

It is permissible for the labels array to contain String values that do not represent any enum constants at runtime.

Parameters:

lookup - the full-privilege lookup context of the caller

invocationName - unused, null is permitted

invocationType - The invocation type of the CallSite with two parameters, an enum type, an int, and int as a return type.

labels - case labels - String constants and Class instances, in any combination

Returns:

a CallSite returning the first matching element as described above

Throws:

IllegalArgumentException - if any element in the labels array is null

IllegalArgumentException - if any element in the labels array is an empty String

IllegalArgumentException - if the invocation type is not a method type whose first parameter type is an enum type, second parameter of type int and whose return type is int

IllegalArgumentException - if labels contains an element that is not of type String or Class equal to the target enum type

See Java Virtual Machine Specification:

4.4.6 The CONSTANT_NameAndType_info Structure
4.4.10 The CONSTANT_Dynamic_info and CONSTANT_InvokeDynamic_info Structures