# Class MethodGen

java.lang.Object
org.apache.bcel.classfile.AccessFlags
org.apache.bcel.generic.FieldGenOrMethodGen
org.apache.bcel.generic.MethodGen

All Implemented Interfaces:
  `Cloneable, NamedAndTyped`

public class MethodGen extends FieldGenOrMethodGen
Template class for building up a method. This is done by defining exception handlers, adding thrown exceptions, local variables and attributes, whereas the 'LocalVariableTable' and 'LineNumberTable' attributes will be set automatically for the code. Use stripAttributes() if you don't like this. While generating code it may be necessary to insert NOP operations. You can use the 'removeNOPs' method to get rid off them. The resulting method object can be obtained via the 'getMethod()' method.

See Also:
  - `InstructionList`
  - `Method`

- ## Field Summary

  ### Fields inherited from class FieldGenOrMethodGen

  `cp, name, type`

  ### Fields inherited from class AccessFlags

  `access_flags`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `MethodGen(int accessFlags, Type returnType, Type[] argTypes, String[] argNames, String methodName, String className, InstructionList il, ConstantPoolGen cp)`
  Declare method.
  `MethodGen(Method method, String className, ConstantPoolGen cp)`
  Instantiate from existing method.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addAnnotationsAsAttribute(ConstantPoolGen cp)`
  `void`
  `addCodeAttribute(Attribute a)`
  Add an attribute to the code.
  `void`
  `addException(String className)`
  Add an exception possibly thrown by this method.
  `CodeExceptionGen`
  `addExceptionHandler(InstructionHandle startPc, InstructionHandle endPc, InstructionHandle handlerPc, ObjectType catchType)`
  Add an exception handler, i.e., specify region where a handler is active and an instruction where the actual handling is done.
  `LineNumberGen`
  `addLineNumber(InstructionHandle ih, int srcLine)`
  Give an instruction a line number corresponding to the source code line.
  `LocalVariableGen`
  `addLocalVariable(String name, Type type, int slot, InstructionHandle start, InstructionHandle end)`
  Adds a local variable to this method.
  `LocalVariableGen`
  `addLocalVariable(String name, Type type, int slot, InstructionHandle start, InstructionHandle end, int origIndex)`
  Adds a local variable to this method.
  `LocalVariableGen`
  `addLocalVariable(String name, Type type, InstructionHandle start, InstructionHandle end)`
  Adds a local variable to this method and assigns an index automatically.
  `void`
  `addObserver(MethodObserver o)`
  Add observer for this object.
  `void`
  `addParameterAnnotation(int parameterIndex, AnnotationEntryGen annotation)`
  `void`
  `addParameterAnnotationsAsAttribute(ConstantPoolGen cp)`
  `MethodGen`
  `copy(String className, ConstantPoolGen cp)`
  `boolean`
  `equals(Object obj)`
  Return value as defined by given BCELComparator strategy.
  `List<AnnotationEntryGen>`
  `getAnnotationsOnParameter(int i)`
  Return a list of AnnotationGen objects representing parameter annotations
  `String`
  `getArgumentName(int i)`
  `String[]`
  `getArgumentNames()`
  `Type`
  `getArgumentType(int i)`
  `Type[]`
  `getArgumentTypes()`
  `String`
  `getClassName()`
  `Attribute[]`
  `getCodeAttributes()`
  `static BCELComparator<FieldGenOrMethodGen>`
  `getComparator()`
  `CodeExceptionGen[]`
  `getExceptionHandlers()`
  `String[]`
  `getExceptions()`
  `InstructionList`
  `getInstructionList()`
  `LineNumberGen[]`
  `getLineNumbers()`
  `LineNumberTable`
  `getLineNumberTable(ConstantPoolGen cp)`
  `LocalVariableGen[]`
  `getLocalVariables()`
  `LocalVariableTable`
  `getLocalVariableTable(ConstantPoolGen cp)`
  `LocalVariableTypeTable`
  `getLocalVariableTypeTable()`
  `int`
  `getMaxLocals()`
  `int`
  `getMaxStack()`
  `static int`
  `getMaxStack(ConstantPoolGen cp, InstructionList il, CodeExceptionGen[] et)`
  Computes stack usage of an instruction list by performing control flow analysis.
  `Method`
  `getMethod()`
  Gets method object.
  `Type`
  `getReturnType()`
  `String`
  `getSignature()`
  `int`
  `hashCode()`
  Return value as defined by given BCELComparator strategy.
  `void`
  `removeCodeAttribute(Attribute a)`
  Remove a code attribute.
  `void`
  `removeCodeAttributes()`
  Remove all code attributes.
  `void`
  `removeException(String c)`
  Remove an exception.
  `void`
  `removeExceptionHandler(CodeExceptionGen c)`
  Remove an exception handler.
  `void`
  `removeExceptionHandlers()`
  Remove all line numbers.
  `void`
  `removeExceptions()`
  Remove all exceptions.
  `void`
  `removeLineNumber(LineNumberGen l)`
  Remove a line number.
  `void`
  `removeLineNumbers()`
  Remove all line numbers.
  `void`
  `removeLocalVariable(LocalVariableGen l)`
  Remove a local variable, its slot will not be reused, if you do not use addLocalVariable with an explicit index argument.
  `void`
  `removeLocalVariables()`
  Remove all local variables.
  `void`
  `removeLocalVariableTypeTable()`
  Remove the LocalVariableTypeTable
  `void`
  `removeNOPs()`
  Remove all NOPs from the instruction list (if possible) and update every object referring to them, i.e., branch instructions, local variables and exception handlers.
  `void`
  `removeObserver(MethodObserver o)`
  Remove observer for this object.
  `void`
  `removeRuntimeAttributes(Attribute[] attributes)`
  Would prefer to make this private, but need a way to test if client is using BCEL version 6.5.0 or later that contains fix for BCEL-329.
  `void`
  `setArgumentName(int i, String name)`
  `void`
  `setArgumentNames(String[] argNames)`
  `void`
  `setArgumentType(int i, Type type)`
  `void`
  `setArgumentTypes(Type[] argTypes)`
  `void`
  `setClassName(String className)`
  `static void`
  `setComparator(BCELComparator<FieldGenOrMethodGen> comparator)`
  `void`
  `setInstructionList(InstructionList il)`
  `void`
  `setMaxLocals()`
  Compute maximum number of local variables.
  `void`
  `setMaxLocals(int m)`
  Sets maximum number of local variables.
  `void`
  `setMaxStack()`
  Computes max. stack size by performing control flow analysis.
  `void`
  `setMaxStack(int m)`
  Sets maximum stack size for this method.
  `void`
  `setReturnType(Type returnType)`
  `void`
  `stripAttributes(boolean flag)`
  Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O
  `final String`
  `toString()`
  Return string representation close to declaration format, 'public static void main(String[]) throws IOException', for example.
  `void`
  `update()`
  Call notify() method on all observers.

  ### Methods inherited from class FieldGenOrMethodGen

  `addAll, addAnnotationEntry, addAttribute, clone, getAnnotationEntries, getAttributes, getConstantPool, getName, getType, removeAnnotationEntries, removeAnnotationEntry, removeAttribute, removeAttributes, setConstantPool, setName, setType`

  ### Methods inherited from class AccessFlags

  `getAccessFlags, getModifiers, isAbstract, isAbstract, isAnnotation, isAnnotation, isEnum, isEnum, isFinal, isFinal, isInterface, isInterface, isNative, isNative, isPrivate, isPrivate, isProtected, isProtected, isPublic, isPublic, isStatic, isStatic, isStrictfp, isStrictfp, isSynchronized, isSynchronized, isSynthetic, isSynthetic, isTransient, isTransient, isVarArgs, isVarArgs, isVolatile, isVolatile, setAccessFlags, setModifiers`

  ### Methods inherited from class Object

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

- ## Constructor Details

  - ### MethodGen

    public MethodGen(int accessFlags, Type returnType, Type[] argTypes, String[] argNames, String methodName, String className, InstructionList il, ConstantPoolGen cp)
    Declare method. If the method is non-static the constructor automatically declares a local variable '$this' in slot 0. The actual code is contained in the 'il' parameter, which may further manipulated by the user. But they must take care not to remove any instruction (handles) that are still referenced from this object. For example one may not add a local variable and later remove the instructions it refers to without causing havoc. It is safe however if you remove that local variable, too.
    Parameters:
      `accessFlags` - access qualifiers
      `returnType` - method type
      `argTypes` - argument types
      `argNames` - argument names (if this is null, default names will be provided for them)
      `methodName` - name of method
      `className` - class name containing this method (may be null, if you don't care)
      `il` - instruction list associated with this method, may be null only for abstract or native methods
      `cp` - constant pool

  - ### MethodGen

    public MethodGen(Method method, String className, ConstantPoolGen cp)
    Instantiate from existing method.
    Parameters:
      `method` - method
      `className` - class name containing this method
      `cp` - constant pool

- ## Method Details

  - ### getComparator

    public static BCELComparator<FieldGenOrMethodGen> getComparator()
    Returns:
      Comparison strategy object.

  - ### getMaxStack

    public static int getMaxStack(ConstantPoolGen cp, InstructionList il, CodeExceptionGen[] et)
    Computes stack usage of an instruction list by performing control flow analysis.
    Returns:
      maximum stack depth used by method

  - ### setComparator

    public static void setComparator(BCELComparator<FieldGenOrMethodGen> comparator)
    Parameters:
      `comparator` - Comparison strategy object.

  - ### addAnnotationsAsAttribute

    public void addAnnotationsAsAttribute(ConstantPoolGen cp)
    Since:
      6.0

  - ### addCodeAttribute

    public void addCodeAttribute(Attribute a)
    Add an attribute to the code. Currently, the JVM knows about the LineNumberTable, LocalVariableTable and StackMap attributes, where the former two will be generated automatically and the latter is used for the MIDP only. Other attributes will be ignored by the JVM but do no harm.
    Parameters:
      `a` - attribute to be added

  - ### addException

    public void addException(String className)
    Add an exception possibly thrown by this method.
    Parameters:
      `className` - (fully qualified) name of exception

  - ### addExceptionHandler

    public CodeExceptionGen addExceptionHandler(InstructionHandle startPc, InstructionHandle endPc, InstructionHandle handlerPc, ObjectType catchType)
    Add an exception handler, i.e., specify region where a handler is active and an instruction where the actual handling is done.
    Parameters:
      `startPc` - Start of region (inclusive)
      `endPc` - End of region (inclusive)
      `handlerPc` - Where handling is done
      `catchType` - class type of handled exception or null if any exception is handled
    Returns:
      new exception handler object

  - ### addLineNumber

    public LineNumberGen addLineNumber(InstructionHandle ih, int srcLine)
    Give an instruction a line number corresponding to the source code line.
    Parameters:
      `ih` - instruction to tag
    Returns:
      new line number object
    See Also:
      - `LineNumber`

  - ### addLocalVariable

    public LocalVariableGen addLocalVariable(String name, Type type, InstructionHandle start, InstructionHandle end)
    Adds a local variable to this method and assigns an index automatically.
    Parameters:
      `name` - variable name
      `type` - variable type
      `start` - from where the variable is valid, if this is null, it is valid from the start
      `end` - until where the variable is valid, if this is null, it is valid to the end
    Returns:
      new local variable object
    See Also:
      - `LocalVariable`

  - ### addLocalVariable

    public LocalVariableGen addLocalVariable(String name, Type type, int slot, InstructionHandle start, InstructionHandle end)
    Adds a local variable to this method.
    Parameters:
      `name` - variable name
      `type` - variable type
      `slot` - the index of the local variable, if type is long or double, the next available index is slot+2
      `start` - from where the variable is valid
      `end` - until where the variable is valid
    Returns:
      new local variable object
    See Also:
      - `LocalVariable`

  - ### addLocalVariable

    public LocalVariableGen addLocalVariable(String name, Type type, int slot, InstructionHandle start, InstructionHandle end, int origIndex)
    Adds a local variable to this method.
    Parameters:
      `name` - variable name
      `type` - variable type
      `slot` - the index of the local variable, if type is long or double, the next available index is slot+2
      `start` - from where the variable is valid
      `end` - until where the variable is valid
      `origIndex` - the index of the local variable prior to any modifications
    Returns:
      new local variable object
    See Also:
      - `LocalVariable`

  - ### addObserver

    public void addObserver(MethodObserver o)
    Add observer for this object.

  - ### addParameterAnnotation

    public void addParameterAnnotation(int parameterIndex, AnnotationEntryGen annotation)

  - ### addParameterAnnotationsAsAttribute

    public void addParameterAnnotationsAsAttribute(ConstantPoolGen cp)
    Since:
      6.0

  - ### copy

    public MethodGen copy(String className, ConstantPoolGen cp)
    Returns:
      deep copy of this method

  - ### equals

    public boolean equals(Object obj)
    Return value as defined by given BCELComparator strategy. By default two MethodGen objects are said to be equal when their names and signatures are equal.
    Overrides:
      `equals` in class `Object`
    See Also:
      - `Object.equals(Object)`

  - ### getAnnotationsOnParameter

    public List<AnnotationEntryGen> getAnnotationsOnParameter(int i)
    Return a list of AnnotationGen objects representing parameter annotations
    Since:
      6.0

  - ### getArgumentName

    public String getArgumentName(int i)

  - ### getArgumentNames

    public String[] getArgumentNames()

  - ### getArgumentType

    public Type getArgumentType(int i)

  - ### getArgumentTypes

    public Type[] getArgumentTypes()

  - ### getClassName

    public String getClassName()
    Returns:
      class that contains this method

  - ### getCodeAttributes

    public Attribute[] getCodeAttributes()
    Returns:
      all attributes of this method.

  - ### getExceptionHandlers

    public CodeExceptionGen[] getExceptionHandlers()

  - ### getExceptions

    public String[] getExceptions()

  - ### getInstructionList

    public InstructionList getInstructionList()

  - ### getLineNumbers

    public LineNumberGen[] getLineNumbers()

  - ### getLineNumberTable

    public LineNumberTable getLineNumberTable(ConstantPoolGen cp)
    Returns:
      'LineNumberTable' attribute of all the local variables of this method.

  - ### getLocalVariables

    public LocalVariableGen[] getLocalVariables()

  - ### getLocalVariableTable

    public LocalVariableTable getLocalVariableTable(ConstantPoolGen cp)
    Returns:
      'LocalVariableTable' attribute of all the local variables of this method.

  - ### getLocalVariableTypeTable

    public LocalVariableTypeTable getLocalVariableTypeTable()
    Returns:
      'LocalVariableTypeTable' attribute of this method.

  - ### getMaxLocals

    public int getMaxLocals()

  - ### getMaxStack

    public int getMaxStack()

  - ### getMethod

    public Method getMethod()
    Gets method object. Never forget to call setMaxStack() or setMaxStack(max), respectively, before calling this method (the same applies for max locals).
    Returns:
      method object

  - ### getReturnType

    public Type getReturnType()

  - ### getSignature

    public String getSignature()
    Specified by:
      `getSignature` in class `FieldGenOrMethodGen`
    Returns:
      signature of method/field.

  - ### hashCode

    public int hashCode()
    Return value as defined by given BCELComparator strategy. By default return the hash code of the method's name XOR signature.
    Overrides:
      `hashCode` in class `Object`
    See Also:
      - `Object.hashCode()`

  - ### removeCodeAttribute

    public void removeCodeAttribute(Attribute a)
    Remove a code attribute.

  - ### removeCodeAttributes

    public void removeCodeAttributes()
    Remove all code attributes.

  - ### removeException

    public void removeException(String c)
    Remove an exception.

  - ### removeExceptionHandler

    public void removeExceptionHandler(CodeExceptionGen c)
    Remove an exception handler.

  - ### removeExceptionHandlers

    public void removeExceptionHandlers()
    Remove all line numbers.

  - ### removeExceptions

    public void removeExceptions()
    Remove all exceptions.

  - ### removeLineNumber

    public void removeLineNumber(LineNumberGen l)
    Remove a line number.

  - ### removeLineNumbers

    public void removeLineNumbers()
    Remove all line numbers.

  - ### removeLocalVariable

    public void removeLocalVariable(LocalVariableGen l)
    Remove a local variable, its slot will not be reused, if you do not use addLocalVariable with an explicit index argument.

  - ### removeLocalVariables

    public void removeLocalVariables()
    Remove all local variables.

  - ### removeLocalVariableTypeTable

    public void removeLocalVariableTypeTable()
    Remove the LocalVariableTypeTable

  - ### removeNOPs

    public void removeNOPs()
    Remove all NOPs from the instruction list (if possible) and update every object referring to them, i.e., branch instructions, local variables and exception handlers.

  - ### removeObserver

    public void removeObserver(MethodObserver o)
    Remove observer for this object.

  - ### removeRuntimeAttributes

    public void removeRuntimeAttributes(Attribute[] attributes)
    Would prefer to make this private, but need a way to test if client is using BCEL version 6.5.0 or later that contains fix for BCEL-329.
    Since:
      6.5.0

  - ### setArgumentName

    public void setArgumentName(int i, String name)

  - ### setArgumentNames

    public void setArgumentNames(String[] argNames)

  - ### setArgumentType

    public void setArgumentType(int i, Type type)

  - ### setArgumentTypes

    public void setArgumentTypes(Type[] argTypes)

  - ### setClassName

    public void setClassName(String className)

  - ### setInstructionList

    public void setInstructionList(InstructionList il)

  - ### setMaxLocals

    public void setMaxLocals()
    Compute maximum number of local variables.

  - ### setMaxLocals

    public void setMaxLocals(int m)
    Sets maximum number of local variables.

  - ### setMaxStack

    public void setMaxStack()
    Computes max. stack size by performing control flow analysis.

  - ### setMaxStack

    public void setMaxStack(int m)
    Sets maximum stack size for this method.

  - ### setReturnType

    public void setReturnType(Type returnType)

  - ### stripAttributes

    public void stripAttributes(boolean flag)
    Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O

  - ### toString

    public final String toString()
    Return string representation close to declaration format, 'public static void main(String[]) throws IOException', for example.
    Overrides:
      `toString` in class `Object`
    Returns:
      String representation of the method.

  - ### update

    public void update()
    Call notify() method on all observers. This method is not called automatically whenever the state has changed, but has to be called by the user after they have finished editing the object.