Package javassist.bytecode.analysis
Class Type
- java.lang.Object
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- javassist.bytecode.analysis.Type
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- Direct Known Subclasses:
MultiArrayType
,MultiType
public class Type extends java.lang.Object
Represents a JVM type in data-flow analysis. This abstraction is necessary since a JVM type not only includes all normal Java types, but also a few special types that are used by the JVM internally. See the static field types on this class for more info on these special types. All primitive and special types reuse the same instance, so identity comparison can be used when examining them. Normal java types must useequals(Object)
to compare type instances. In most cases, applications which consume this API, only need to callgetCtClass()
to obtain the needed type information.- Author:
- Jason T. Greene
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Field Summary
Fields Modifier and Type Field Description static Type
BOGUS
Represents a non-accessible value.static Type
BOOLEAN
Represents the boolean primitive typestatic Type
BYTE
Represents the byte primitive typestatic Type
CHAR
Represents the char primitive typestatic Type
CLONEABLE
Represents the java.lang.Coneable reference typestatic Type
DOUBLE
Represents the double primitive typestatic Type
FLOAT
Represents the float primitive typestatic Type
INTEGER
Represents the integer primitive typestatic Type
LONG
Represents the long primitive typestatic Type
OBJECT
Represents the java.lang.Object reference typestatic Type
RETURN_ADDRESS
Represents an internal JVM return address, which is used by the RET instruction to return to a JSR that invoked the subroutine.static Type
SERIALIZABLE
Represents the java.io.Serializable reference typestatic Type
SHORT
Represents the short primitive typestatic Type
THROWABLE
Represents the java.lang.Throwable reference typestatic Type
TOP
A placeholder used by the analyzer for the second word position of a double-word typestatic Type
UNINIT
Represents an unknown, or null type.static Type
VOID
Represents the void primitive type
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
equals(java.lang.Object o)
static Type
get(CtClass clazz)
Obtain the Type for a given class.Type
getComponent()
Returns the array component if this type is an array.CtClass
getCtClass()
Returns the class this type represents.int
getDimensions()
Returns the number of dimensions of this array.int
getSize()
Gets the word size of this type.int
hashCode()
boolean
isArray()
Returns whether or not this type is an array.boolean
isAssignableFrom(Type type)
Determines whether this type is assignable, to the passed type.boolean
isReference()
Returns whether or not this type is a normal java reference, i.e.boolean
isSpecial()
Returns whether or not the type is special.Type
merge(Type type)
Finds the common base type, or interface which both this and the specified type can be assigned.java.lang.String
toString()
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Field Detail
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DOUBLE
public static final Type DOUBLE
Represents the double primitive type
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BOOLEAN
public static final Type BOOLEAN
Represents the boolean primitive type
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LONG
public static final Type LONG
Represents the long primitive type
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CHAR
public static final Type CHAR
Represents the char primitive type
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BYTE
public static final Type BYTE
Represents the byte primitive type
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SHORT
public static final Type SHORT
Represents the short primitive type
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INTEGER
public static final Type INTEGER
Represents the integer primitive type
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FLOAT
public static final Type FLOAT
Represents the float primitive type
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VOID
public static final Type VOID
Represents the void primitive type
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UNINIT
public static final Type UNINIT
Represents an unknown, or null type. This occurs when aconst_null is used. It is important not to treat this type as java.lang.Object, since a null can be assigned to any reference type. The analyzer will replace these with an actual known type if it can be determined by a merged path with known type information. If this type is encountered on a frame then it is guaranteed to be null, and the type information is simply not available. Any attempts to infer the type, without further information from the compiler would be a guess.
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RETURN_ADDRESS
public static final Type RETURN_ADDRESS
Represents an internal JVM return address, which is used by the RET instruction to return to a JSR that invoked the subroutine.
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TOP
public static final Type TOP
A placeholder used by the analyzer for the second word position of a double-word type
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BOGUS
public static final Type BOGUS
Represents a non-accessible value. Code cannot access the value this type represents. It occurs when bytecode reuses a local variable table position with non-mergable types. An example would be compiled code which uses the same position for a primitive type in one branch, and a reference type in another branch.
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OBJECT
public static final Type OBJECT
Represents the java.lang.Object reference type
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SERIALIZABLE
public static final Type SERIALIZABLE
Represents the java.io.Serializable reference type
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CLONEABLE
public static final Type CLONEABLE
Represents the java.lang.Coneable reference type
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THROWABLE
public static final Type THROWABLE
Represents the java.lang.Throwable reference type
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Method Detail
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get
public static Type get(CtClass clazz)
Obtain the Type for a given class. If the class is a primitive, the the unique type instance for the primitive will be returned. Otherwise a new Type instance representing the class is returned.- Parameters:
clazz
- The java class- Returns:
- a type instance for this class
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getSize
public int getSize()
Gets the word size of this type. Double-word types, such as long and double will occupy two positions on the local variable table or stack.- Returns:
- the number of words needed to hold this type
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getCtClass
public CtClass getCtClass()
Returns the class this type represents. If the type is special, null will be returned.- Returns:
- the class for this type, or null if special
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isReference
public boolean isReference()
Returns whether or not this type is a normal java reference, i.e. it is or extends java.lang.Object.- Returns:
- true if a java reference, false if a primitive or special
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isSpecial
public boolean isSpecial()
Returns whether or not the type is special. A special type is one that is either used for internal tracking, or is only used internally by the JVM.- Returns:
- true if special, false if not
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isArray
public boolean isArray()
Returns whether or not this type is an array.- Returns:
- true if an array, false if not
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getDimensions
public int getDimensions()
Returns the number of dimensions of this array. If the type is not an array zero is returned.- Returns:
- zero if not an array, otherwise the number of array dimensions.
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getComponent
public Type getComponent()
Returns the array component if this type is an array. If the type is not an array null is returned.- Returns:
- the array component if an array, otherwise null
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isAssignableFrom
public boolean isAssignableFrom(Type type)
Determines whether this type is assignable, to the passed type. A type is assignable to another if it is either the same type, or a sub-type.- Parameters:
type
- the type to test assignability to- Returns:
- true if this is assignable to type, otherwise false
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merge
public Type merge(Type type)
Finds the common base type, or interface which both this and the specified type can be assigned. If there is more than one possible answer, then aMultiType
, or aMultiArrayType
is returned. Multi-types have special rules, and successive merges and assignment tests on them will alter their internal state, as well as other multi-types they have been merged with. This method is used by the data-flow analyzer to merge the type state from multiple branches.- Parameters:
type
- the type to merge with- Returns:
- the merged type
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hashCode
public int hashCode()
- Overrides:
hashCode
in classjava.lang.Object
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equals
public boolean equals(java.lang.Object o)
- Overrides:
equals
in classjava.lang.Object
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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