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org.apache.bcel.verifier.structurals
Class Frame  

java.lang.Object
  org.apache.bcel.verifier.structurals.Frame

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public class Frame

extends java.lang.Object

This class represents a JVM execution frame; that means, a local variable array and an operand stack.

Version:

$Id: Frame.java 386056 2006-03-15 11:31:56Z tcurdt $

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Field Summary
protected static UninitializedObjectType	_this           For instance initialization methods, it is important to remember which instance it is that is not initialized yet.
private  LocalVariables	locals
private  OperandStack	stack

 

Constructor Summary

Frame(int maxLocals, int maxStack)

Frame(LocalVariables locals, OperandStack stack)

 

Method Summary
protected  java.lang.Object	clone()           This method may be called to create a new copy of the Object.
boolean	equals(java.lang.Object o)           Determine whether this Object is semantically equal to another Object.
Frame	getClone()
LocalVariables	getLocals()
OperandStack	getStack()
int	hashCode()           Get a value that represents this Object, as uniquely as possible within the confines of an int.
java.lang.String	toString()           Returns a String representation of the Frame instance.

 

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

 

Field Detail

_this

protected static UninitializedObjectType _this

For instance initialization methods, it is important to remember which instance it is that is not initialized yet. It will be initialized invoking another constructor later. NULL means the instance already *is* initialized.

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locals

private LocalVariables locals

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stack

private OperandStack stack

Constructor Detail

Frame

public Frame(int maxLocals,
             int maxStack)

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Frame

public Frame(LocalVariables locals,
             OperandStack stack)

Method Detail

clone

protected java.lang.Object clone()

Description copied from class: java.lang.Object

This method may be called to create a new copy of the Object. The typical behavior is as follows:

• o == o.clone() is false
• o.getClass() == o.clone().getClass() is true
• o.equals(o) is true

However, these are not strict requirements, and may be violated if necessary. Of the three requirements, the last is the most commonly violated, particularly if the subclass does not override Object.equals(Object)>Object.equals(Object) 55 .

If the Object you call clone() on does not implement java.lang.Cloneable (which is a placeholder interface), then a CloneNotSupportedException is thrown. Notice that Object does not implement Cloneable; this method exists as a convenience for subclasses that do.

Object's implementation of clone allocates space for the new Object using the correct class, without calling any constructors, and then fills in all of the new field values with the old field values. Thus, it is a shallow copy. However, subclasses are permitted to make a deep copy.

All array types implement Cloneable, and override this method as follows (it should never fail):

 public Object clone()
 {
   try
     {
       super.clone();
     }
   catch (CloneNotSupportedException e)
     {
       throw new InternalError(e.getMessage());
     }
 }
 

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getClone

public Frame getClone()

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getLocals

public LocalVariables getLocals()

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getStack

public OperandStack getStack()

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hashCode

public int hashCode()

Description copied from class: java.lang.Object

Get a value that represents this Object, as uniquely as possible within the confines of an int.

There are some requirements on this method which subclasses must follow:

• Semantic equality implies identical hashcodes. In other words, if a.equals(b) is true, then a.hashCode() == b.hashCode() must be as well. However, the reverse is not necessarily true, and two objects may have the same hashcode without being equal.
• It must be consistent. Whichever value o.hashCode() returns on the first invocation must be the value returned on all later invocations as long as the object exists. Notice, however, that the result of hashCode may change between separate executions of a Virtual Machine, because it is not invoked on the same object.

Notice that since hashCode is used in java.util.Hashtable and other hashing classes, a poor implementation will degrade the performance of hashing (so don't blindly implement it as returning a constant!). Also, if calculating the hash is time-consuming, a class may consider caching the results.

The default implementation returns System.identityHashCode(this)

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equals

public boolean equals(java.lang.Object o)

Description copied from class: java.lang.Object

Determine whether this Object is semantically equal to another Object.

There are some fairly strict requirements on this method which subclasses must follow:

• It must be transitive. If a.equals(b) and b.equals(c), then a.equals(c) must be true as well.
• It must be symmetric. a.equals(b) and b.equals(a) must have the same value.
• It must be reflexive. a.equals(a) must always be true.
• It must be consistent. Whichever value a.equals(b) returns on the first invocation must be the value returned on all later invocations.
• a.equals(null) must be false.
• It must be consistent with hashCode(). That is, a.equals(b) must imply a.hashCode() == b.hashCode(). The reverse is not true; two objects that are not equal may have the same hashcode, but that has the potential to harm hashing performance.

This is typically overridden to throw a java.lang.ClassCastException if the argument is not comparable to the class performing the comparison, but that is not a requirement. It is legal for a.equals(b) to be true even though a.getClass() != b.getClass(). Also, it is typical to never cause a java.lang.NullPointerException.

In general, the Collections API (java.util) use the equals method rather than the == operator to compare objects. However, java.util.IdentityHashMap is an exception to this rule, for its own good reasons.

The default implementation returns this == o.

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toString

public java.lang.String toString()

Returns a String representation of the Frame instance.

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Home >> All >> org >> apache >> bcel >> verifier >> [ structurals overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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