org.apache.bcel.generic

## 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.
  Version:
    $Id: MethodGen.java 1812710 2017-10-20 06:24:15Z kinow $
  See Also:
    `InstructionList`, `Method`

- - ### Field Summary

    - ### Fields inherited from class org.apache.bcel.generic.FieldGenOrMethodGen

      `cp, name, type`

    - ### Fields inherited from class org.apache.bcel.classfile.AccessFlags

      `access_flags`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `MethodGen(int access_flags, Type return_type, Type[] arg_types, String[] arg_names, String method_name, String class_name, InstructionList il, ConstantPoolGen cp)` Declare method.
    `MethodGen(Method m, String class_name, ConstantPoolGen cp)` Instantiate from existing method.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addAnnotationsAsAttribute(ConstantPoolGen cp)`
    `void` | `addCodeAttribute(Attribute a)` Add an attribute to the code.
    `void` | `addException(String class_name)` Add an exception possibly thrown by this method.
    `CodeExceptionGen` | `addExceptionHandler(InstructionHandle start_pc, InstructionHandle end_pc, InstructionHandle handler_pc, ObjectType catch_type)` 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 src_line)` Give an instruction a line number corresponding to the source code line.
    `LocalVariableGen` | `addLocalVariable(String name, Type type, InstructionHandle start, InstructionHandle end)` Adds a local variable to this method and assigns an index automatically.
    `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 orig_index)` Adds a local variable to this method.
    `void` | `addObserver(MethodObserver o)` Add observer for this object.
    `void` | `addParameterAnnotation(int parameterIndex, AnnotationEntryGen annotation)`
    `void` | `addParameterAnnotationsAsAttribute(ConstantPoolGen cp)`
    `MethodGen` | `copy(String class_name, 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` | `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()` Get 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` | `setArgumentName(int i, String name)`
    `void` | `setArgumentNames(String[] arg_names)`
    `void` | `setArgumentType(int i, Type type)`
    `void` | `setArgumentTypes(Type[] arg_types)`
    `void` | `setClassName(String class_name)`
    `static void` | `setComparator(BCELComparator comparator)`
    `void` | `setInstructionList(InstructionList il)`
    `void` | `setMaxLocals()` Compute maximum number of local variables.
    `void` | `setMaxLocals(int m)` Set maximum number of local variables.
    `void` | `setMaxStack()` Computes max.
    `void` | `setMaxStack(int m)` Set maximum stack size for this method.
    `void` | `setReturnType(Type return_type)`
    `void` | `stripAttributes(boolean flag)` Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O
    `String` | `toString()` Return string representation close to declaration format, `public static void main(String[]) throws IOException', e.g.
    `void` | `update()` Call notify() method on all observers.

    - ### Methods inherited from class org.apache.bcel.generic.FieldGenOrMethodGen

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

    - ### Methods inherited from class org.apache.bcel.classfile.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 java.lang.Object

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

- - ### Constructor Detail

    - #### MethodGen

          public MethodGen(int access_flags,
                           Type return_type,
                           Type[] arg_types,
                           String[] arg_names,
                           String method_name,
                           String class_name,
                           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 he 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:
        `access_flags` - access qualifiers
        `return_type` - method type
        `arg_types` - argument types
        `arg_names` - argument names (if this is null, default names will be provided for them)
        `method_name` - name of method
        `class_name` - 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 m,
                           String class_name,
                           ConstantPoolGen cp)

      Instantiate from existing method.
      Parameters:
        `m` - method
        `class_name` - class name containing this method
        `cp` - constant pool

  - ### Method Detail

    - #### addLocalVariable

          public LocalVariableGen addLocalVariable(String name,
                                                   Type type,
                                                   int slot,
                                                   InstructionHandle start,
                                                   InstructionHandle end,
                                                   int orig_index)

      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
        `orig_index` - the index of the local variable prior to any modifications
      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,
                                                   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`

    - #### 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.

    - #### 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.

    - #### addLineNumber

          public LineNumberGen addLineNumber(InstructionHandle ih,
                                             int src_line)

      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`

    - #### removeLineNumber

          public void removeLineNumber(LineNumberGen l)

      Remove a line number.

    - #### removeLineNumbers

          public void removeLineNumbers()

      Remove all line numbers.

    - #### getLineNumbers

          public LineNumberGen[] getLineNumbers()

    - #### getLineNumberTable

          public LineNumberTable getLineNumberTable(ConstantPoolGen cp)

      Returns:
        `LineNumberTable' attribute of all the local variables of this method.

    - #### addExceptionHandler

          public CodeExceptionGen addExceptionHandler(InstructionHandle start_pc,
                                                      InstructionHandle end_pc,
                                                      InstructionHandle handler_pc,
                                                      ObjectType catch_type)

      Add an exception handler, i.e., specify region where a handler is active and an instruction where the actual handling is done.
      Parameters:
        `start_pc` - Start of region (inclusive)
        `end_pc` - End of region (inclusive)
        `handler_pc` - Where handling is done
        `catch_type` - class type of handled exception or null if any exception is handled
      Returns:
        new exception handler object

    - #### removeExceptionHandler

          public void removeExceptionHandler(CodeExceptionGen c)

      Remove an exception handler.

    - #### removeExceptionHandlers

          public void removeExceptionHandlers()

      Remove all line numbers.

    - #### getExceptionHandlers

          public CodeExceptionGen[] getExceptionHandlers()

    - #### addException

          public void addException(String class_name)

      Add an exception possibly thrown by this method.
      Parameters:
        `class_name` - (fully qualified) name of exception

    - #### removeException

          public void removeException(String c)

      Remove an exception.

    - #### removeExceptions

          public void removeExceptions()

      Remove all exceptions.

    - #### getExceptions

          public String[] getExceptions()

    - #### 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

    - #### removeLocalVariableTypeTable

          public void removeLocalVariableTypeTable()

      Remove the LocalVariableTypeTable

    - #### removeCodeAttribute

          public void removeCodeAttribute(Attribute a)

      Remove a code attribute.

    - #### removeCodeAttributes

          public void removeCodeAttributes()

      Remove all code attributes.

    - #### getCodeAttributes

          public Attribute[] getCodeAttributes()

      Returns:
        all attributes of this method.

    - #### addAnnotationsAsAttribute

          public void addAnnotationsAsAttribute(ConstantPoolGen cp)

      Since:
        6.0

    - #### addParameterAnnotationsAsAttribute

          public void addParameterAnnotationsAsAttribute(ConstantPoolGen cp)

      Since:
        6.0

    - #### getMethod

          public Method getMethod()

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

    - #### 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.

    - #### setMaxLocals

          public void setMaxLocals(int m)

      Set maximum number of local variables.

    - #### getMaxLocals

          public int getMaxLocals()

    - #### setMaxStack

          public void setMaxStack(int m)

      Set maximum stack size for this method.

    - #### getMaxStack

          public int getMaxStack()

    - #### getClassName

          public String getClassName()

      Returns:
        class that contains this method

    - #### setClassName

          public void setClassName(String class_name)

    - #### setReturnType

          public void setReturnType(Type return_type)

    - #### getReturnType

          public Type getReturnType()

    - #### setArgumentTypes

          public void setArgumentTypes(Type[] arg_types)

    - #### getArgumentTypes

          public Type[] getArgumentTypes()

    - #### setArgumentType

          public void setArgumentType(int i,
                                      Type type)

    - #### getArgumentType

          public Type getArgumentType(int i)

    - #### setArgumentNames

          public void setArgumentNames(String[] arg_names)

    - #### getArgumentNames

          public String[] getArgumentNames()

    - #### setArgumentName

          public void setArgumentName(int i,
                                      String name)

    - #### getArgumentName

          public String getArgumentName(int i)

    - #### getInstructionList

          public InstructionList getInstructionList()

    - #### setInstructionList

          public void setInstructionList(InstructionList il)

    - #### getSignature

          public String getSignature()

      Specified by:
        `getSignature` in class `FieldGenOrMethodGen`
      Returns:
        signature of method/field.

    - #### setMaxStack

          public void setMaxStack()

      Computes max. stack size by performing control flow analysis.

    - #### setMaxLocals

          public void setMaxLocals()

      Compute maximum number of local variables.

    - #### stripAttributes

          public void stripAttributes(boolean flag)

      Do not/Do produce attributes code attributesLineNumberTable and LocalVariableTable, like javac -O

    - #### 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

    - #### addObserver

          public void addObserver(MethodObserver o)

      Add observer for this object.

    - #### removeObserver

          public void removeObserver(MethodObserver o)

      Remove observer for this object.

    - #### 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 he has finished editing the object.

    - #### toString

          public final String toString()

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

    - #### copy

          public MethodGen copy(String class_name,
                                ConstantPoolGen cp)

      Returns:
        deep copy of this method

    - #### getAnnotationsOnParameter

          public List<AnnotationEntryGen> getAnnotationsOnParameter(int i)

      Return a list of AnnotationGen objects representing parameter annotations
      Since:
        6.0

    - #### addParameterAnnotation

          public void addParameterAnnotation(int parameterIndex,
                                             AnnotationEntryGen annotation)

    - #### getComparator

          public static BCELComparator getComparator()

      Returns:
        Comparison strategy object

    - #### setComparator

          public static void setComparator(BCELComparator comparator)

      Parameters:
        `comparator` - Comparison strategy object

    - #### 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(java.lang.Object)`

    - #### hashCode

          public int hashCode()

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

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