public class SwitchBootstraps extends Object
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)
.Modifier and Type | Method | Description |
---|---|---|
static CallSite |
enumSwitch |
Bootstrap method for linking an invokedynamic call site that implements a switch on a target of an enum type. |
static CallSite |
typeSwitch |
Bootstrap method for linking an invokedynamic call site that implements a switch on a target of a reference type. |
public static CallSite typeSwitch(MethodHandles.Lookup lookup, String invocationName, MethodType invocationType, Object... labels)
invokedynamic
call site that implements a switch
on a target of a reference type. The static arguments are an array of case labels which must be non-null and of type String
or Integer
or Class
or EnumDesc
. 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 an Object
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:
Class
that is assignable from the target's class; orString
or Integer
and equals to the target.EnumDesc
, that describes a constant that is equals 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.
lookup
- Represents a lookup context with the accessibility privileges of the caller. When used with invokedynamic
, this is stacked automatically by the VM.invocationName
- unusedinvocationType
- The invocation type of the CallSite
with two parameters, a reference type, an int
, and int
as a return type.labels
- case labels - String
and Integer
constants and Class
and EnumDesc
instances, in any combinationCallSite
returning the first matching element as described aboveNullPointerException
- if any argument is null
IllegalArgumentException
- if any element in the labels array is null, if the invocation type is not not a method type of first parameter of a reference type, second parameter of type int
and with int
as its return type, or if labels
contains an element that is not of type String
, Integer
, Class
or EnumDesc
.public static CallSite enumSwitch(MethodHandles.Lookup lookup, String invocationName, MethodType invocationType, Object... labels)
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: String
value, which represents the name of the enum constant associated with the labelClass
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:
Class
that is assignable from the target's class; orString
and equals to the target enum constant's Enum.name()
. 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.
lookup
- Represents a lookup context with the accessibility privileges of the caller. When used with invokedynamic
, this is stacked automatically by the VM.invocationName
- unusedinvocationType
- 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 combinationCallSite
returning the first matching element as described aboveNullPointerException
- if any argument is null
IllegalArgumentException
- if any element in the labels array is null, 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
, or if labels
contains an element that is not of type String
or Class
of the target enum type.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/runtime/SwitchBootstraps.html