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()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()`	Returns a string representation of the object.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

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.

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

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