baload

Operation

Load byte or boolean from array

Format

baload

Forms

baload = 51 (0x33)

Operand Stack

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

Description

The arrayref must be of type reference and must refer to an array whose components are of type byte or of type boolean. The index must be of type int. Both arrayref and index are popped from the operand stack. If the components of the array are of type byte, the component of the array at index is retrieved and sign-extended to an int value. If the components of the array are of type boolean, the component of the array at index is retrieved and zero-extended to an int value. In either case the resulting value is pushed onto the operand stack.

Runtime Exceptions

If arrayref is null, baload throws a NullPointerException.

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

Notes

The baload instruction is used to load values from both byte and boolean arrays. In Sun's implementation of the Java virtual machine, boolean arrays (arrays of type T_BOOLEAN; see §3.2 and the description of the newarray instruction in this chapter) are implemented as arrays of 8-bit values. Other implementations may implement packed boolean arrays; the baload instruction of such implementations must be used to access those arrays.

bastore

Operation

Store into byte or boolean array

Format

bastore

Forms

bastore = 84 (0x54)

Operand Stack

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

Description

The arrayref must be of type reference and must refer to an array whose components are of type byte or of type boolean. The index and the value must both be of type int. The arrayref, index, and value are popped from the operand stack. If the components of the array are of type byte, the int value is truncated to a byte and stored as the component of the array indexed by index. If the components of the array are of type boolean, the int value is truncated to its low order bit then zero-extended to the storage size for components of boolean arrays used by the implementation. The result is stored as the component of the array indexed by index.

Runtime Exceptions

If arrayref is null, bastore throws a NullPointerException.

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

Notes

The bastore instruction is used to store values into both byte and boolean arrays. In Sun's implementation of the Java virtual machine, boolean arrays (arrays of type T_BOOLEAN; see §3.2 and the description of the newarray instruction in this chapter) are implemented as arrays of 8-bit values. Other implementations may implement packed boolean arrays; in such implementations the bastore instruction must be able to store boolean values into packed boolean arrays as well as byte values into byte arrays.

bipush

Operation

Push byte

Format

bipush
byte

Forms

bipush = 16 (0x10)

Operand Stack

... ..., value

Description

The immediate byte is sign-extended to an int value. That value is pushed onto the operand stack.

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The Java^TM Virtual Machine Specification
Copyright © 1999 Sun Microsystems, Inc. All rights reserved
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