caload

Operation

Load char from array

Format

caload

Forms

caload = 52 (0x34)

Operand Stack

..., arrayref, index ..., value

Description

The arrayref must be of type reference and must refer to an array whose components are of type char. The index must be of type int. Both arrayref and index are popped from the operand stack. The component of the array at index is retrieved and zero-extended to an int value. That value is pushed onto the operand stack.

Runtime Exceptions

If arrayref is null, caload throws a NullPointerException.

Otherwise, if index is not within the bounds of the array referenced by arrayref, the caload instruction throws an ArrayIndexOutOfBoundsException.

castore

Operation

Store into char array

Format

castore

Forms

castore = 85 (0x55)

Operand Stack

..., arrayref, index, value ...

Description

The arrayref must be of type reference and must refer to an array whose components are of type char. The index and the value must both be of type int. The arrayref, index, and value are popped from the operand stack. The int value is truncated to a char and stored as the component of the array indexed by index.

Runtime Exceptions

If arrayref is null, castore throws a NullPointerException.

Otherwise, if index is not within the bounds of the array referenced by arrayref, the castore instruction throws an ArrayIndexOutOfBoundsException.

checkcast

Operation

Check whether object is of given type

Format

checkcast
indexbyte1
indexbyte2

Forms

checkcast = 192 (0xc0)

Operand Stack

..., objectref ..., objectref

Description

The objectref must be of type reference. The unsigned indexbyte1 and indexbyte2 are used to construct an index into the runtime constant pool of the current class (§3.6), where the value of the index is (indexbyte1 << 8) | indexbyte2. The runtime constant pool item at the index must be a symbolic reference to a class, array, or interface type. The named class, array, or interface type is resolved (§5.4.3.1).

If objectref is null or can be cast to the resolved class, array, or interface type, the operand stack is unchanged; otherwise, the checkcast instruction throws a ClassCastException.

The following rules are used to determine whether an objectref that is not null can be cast to the resolved type: if S is the class of the object referred to by objectref and T is the resolved class, array, or interface type, checkcast determines whether objectref can be cast to type T as follows:

• If S is an ordinary (nonarray) class, then:
  • If T is a class type, then S must be the same class (§2.8.1) as T, or a subclass of T.

  • If T is an interface type, then S must implement (§2.13) interface T.

• If S is an interface type, then:
  • If T is a class type, then T must be Object (§2.4.7).

  • If T is an interface type, then T must be the same interface as S or a superinterface of S (§2.13.2).

• If S is a class representing the array type SC[], that is, an array of components of type SC, then:
  • If T is a class type, then T must be Object (§2.4.7).

  • If T is an array type TC[], that is, an array of components of type TC, then one of the following must be true:
    • TC and SC are the same primitive type (§2.4.1).

    • TC and SC are reference types (§2.4.6), and type SC can be cast to TC by recursive application of these rules.

  • If T is an interface type, T must be one of the interfaces implemented by arrays (§2.15).

Linking Exceptions

During resolution of the symbolic reference to the class, array, or interface type, any of the exceptions documented in Section 5.4.3.1 can be thrown.

Runtime Exception

Otherwise, if objectref cannot be cast to the resolved class, array, or interface type, the checkcast instruction throws a ClassCastException.

Notes

The checkcast instruction is very similar to the instanceof instruction. It differs in its treatment of null, its behavior when its test fails (checkcast throws an exception, instanceof pushes a result code), and its effect on the operand stack.

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The Java^TM Virtual Machine Specification
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