Create new object
Bytecode
Type | Description |
u1 | new opcode = 0xBB (187) |
u2 | index |
Description
new is used to create object instances. new takes a single parameter, <class>, the name of the class of object you want to create. <class> is resolved into a Java class (see Chapter 7 for a discussion of how classes are resolved). Then new determines the size in bytes of instances of the given class and allocates memory for the new instance from the garbage collected heap. The fields of the instance are set to the initial value 0 (for numeric and boolean fields), or null (for reference fields). Next, a reference to the new object is pushed onto the operand stack.
Note that the new object is initialize uninitialized - before the new object can be used, one of its <init> methods must be called using invokespecial, as shown in the example below.
The unsigned index is used to get access to class entry. The symbolic
reference is resolved and must result in a class type (it must not result in an
array or interface type). Memory for a new instance of that class is allocated from the
garbage-collected heap, and the instance variables of the new object are initialized to
their default initial values . The objectref, a reference
to the
instance, is pushed onto the operand stack.
Example
; This example creates a new StringBuffer object. This is like the Java code: ; ; StringBuffer x = new StringBuffer(); ; 1. use new to create a new object reference new java/lang/StringBuffer ; 2. dup the object reference and call its constructor dup invokespecial java/lang/StringBuffer/<init>()V ; 3. assign object reference on the stack to a local variable astore_1 ; local variable 1 now contains a StringBuffer object, ; ready for use ; the following example shows how to call a non-default ; constructor. It is like the Java code: ; ; StringBuffer x = new StringBuffer(100); new java/lang/StringBuffer dup bipush 100 invokespecial java/lang/StringBuffer/<init>(I)V astore_1
Exceptions
OutOfMemoryError - not enough memory to allocate a new instance
InstantiationError - The class named by <type> is an abstract class or an interface
The new instruction does not completely create a new instance; instance creation is not completed until an instance initialization method has been invoked on the uninitialized instance.