# Class InstructionList

java.lang.Object
org.apache.bcel.generic.InstructionList

All Implemented Interfaces:
  `Iterable<InstructionHandle>`

public class InstructionList extends Object implements Iterable<InstructionHandle>
This class is a container for a list of Instruction objects. Instructions can be appended, inserted, moved, deleted, and so on. Instructions are being wrapped into InstructionHandles objects that are returned upon append/insert operations. They give the user (read only) access to the list structure, such that it can be traversed and manipulated in a controlled way.

A list is finally dumped to a byte code array with getByteCode.

See Also:
  - `Instruction`
  - `InstructionHandle`
  - `BranchHandle`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `InstructionList()`
  Create (empty) instruction list.
  `InstructionList(byte[] code)`
  Initialize instruction list from byte array.
  `InstructionList(BranchInstruction i)`
  Create instruction list containing one instruction.
  `InstructionList(CompoundInstruction c)`
  Initialize list with (nonnull) compound instruction.
  `InstructionList(Instruction i)`
  Create instruction list containing one instruction.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `addObserver(InstructionListObserver o)`
  Add observer for this object.
  `BranchHandle`
  `append(BranchInstruction i)`
  Append a branch instruction to the end of this list.
  `InstructionHandle`
  `append(CompoundInstruction c)`
  Append a compound instruction.
  `InstructionHandle`
  `append(Instruction i)`
  Append an instruction to the end of this list.
  `BranchHandle`
  `append(InstructionHandle ih, BranchInstruction i)`
  Append an instruction after instruction (handle) ih contained in this list.
  `InstructionHandle`
  `append(InstructionHandle ih, CompoundInstruction c)`
  Append a compound instruction.
  `InstructionHandle`
  `append(InstructionHandle ih, Instruction i)`
  Append an instruction after instruction (handle) ih contained in this list.
  `InstructionHandle`
  `append(InstructionHandle ih, InstructionList il)`
  Append another list after instruction (handle) ih contained in this list.
  `InstructionHandle`
  `append(InstructionList il)`
  Append another list to this one.
  `InstructionHandle`
  `append(Instruction i, CompoundInstruction c)`
  Append a compound instruction, after instruction i.
  `InstructionHandle`
  `append(Instruction i, Instruction j)`
  Append a single instruction j after another instruction i, which must be in this list of course!
  `InstructionHandle`
  `append(Instruction i, InstructionList il)`
  Append another list after instruction i contained in this list.
  `boolean`
  `contains(Instruction i)`
  `boolean`
  `contains(InstructionHandle i)`
  `InstructionList`
  `copy()`
  `void`
  `delete(Instruction i)`
  Remove instruction from this list.
  `void`
  `delete(InstructionHandle ih)`
  Remove instruction from this list.
  `void`
  `delete(InstructionHandle from, InstructionHandle to)`
  Remove instructions from instruction 'from' to instruction 'to' contained in this list.
  `void`
  `delete(Instruction from, Instruction to)`
  Remove instructions from instruction 'from' to instruction 'to' contained in this list.
  `void`
  `dispose()`
  Delete contents of list.
  `InstructionHandle`
  `findHandle(int pos)`
  Gets instruction handle for instruction at byte code position pos.
  `static InstructionHandle`
  `findHandle(InstructionHandle[] ihs, int[] pos, int count, int target)`
  Find the target instruction (handle) that corresponds to the given target position (byte code offset).
  `byte[]`
  `getByteCode()`
  When everything is finished, use this method to convert the instruction list into an array of bytes.
  `InstructionHandle`
  `getEnd()`
  `InstructionHandle[]`
  `getInstructionHandles()`
  `int[]`
  `getInstructionPositions()`
  Gets positions (offsets) of all instructions in the list.
  `Instruction[]`
  `getInstructions()`
  `int`
  `getLength()`
  `InstructionHandle`
  `getStart()`
  `BranchHandle`
  `insert(BranchInstruction i)`
  Insert a branch instruction at start of this list.
  `InstructionHandle`
  `insert(CompoundInstruction c)`
  Insert a compound instruction.
  `InstructionHandle`
  `insert(Instruction i)`
  Insert an instruction at start of this list.
  `BranchHandle`
  `insert(InstructionHandle ih, BranchInstruction i)`
  Insert an instruction before instruction (handle) ih contained in this list.
  `InstructionHandle`
  `insert(InstructionHandle ih, CompoundInstruction c)`
  Insert a compound instruction.
  `InstructionHandle`
  `insert(InstructionHandle ih, Instruction i)`
  Insert an instruction before instruction (handle) ih contained in this list.
  `InstructionHandle`
  `insert(InstructionHandle ih, InstructionList il)`
  Insert another list before Instruction handle ih contained in this list.
  `InstructionHandle`
  `insert(InstructionList il)`
  Insert another list.
  `InstructionHandle`
  `insert(Instruction i, CompoundInstruction c)`
  Insert a compound instruction before instruction i.
  `InstructionHandle`
  `insert(Instruction i, Instruction j)`
  Insert a single instruction j before another instruction i, which must be in this list of course!
  `InstructionHandle`
  `insert(Instruction i, InstructionList il)`
  Insert another list before Instruction i contained in this list.
  `boolean`
  `isEmpty()`
  Tests for empty list.
  `Iterator<InstructionHandle>`
  `iterator()`
  `void`
  `move(InstructionHandle ih, InstructionHandle target)`
  Move a single instruction (handle) to a new location.
  `void`
  `move(InstructionHandle start, InstructionHandle end, InstructionHandle target)`
  Take all instructions (handles) from "start" to "end" and append them after the new location "target".
  `void`
  `redirectBranches(InstructionHandle oldTarget, InstructionHandle newTarget)`
  Redirect all references from oldTarget to newTarget, i.e., update targets of branch instructions.
  `void`
  `redirectExceptionHandlers(CodeExceptionGen[] exceptions, InstructionHandle oldTarget, InstructionHandle newTarget)`
  Redirect all references of exception handlers from oldTarget to newTarget.
  `void`
  `redirectLocalVariables(LocalVariableGen[] lg, InstructionHandle oldTarget, InstructionHandle newTarget)`
  Redirect all references of local variables from oldTarget to newTarget.
  `void`
  `removeObserver(InstructionListObserver o)`
  Remove observer for this object.
  `void`
  `replaceConstantPool(ConstantPoolGen oldCp, ConstantPoolGen newCp)`
  Replace all references to the old constant pool with references to the new constant pool
  `void`
  `setPositions()`
  `void`
  `setPositions(boolean check)`
  Give all instructions their position number (offset in byte stream), i.e., make the list ready to be dumped.
  `int`
  `size()`
  `String`
  `toString()`
  `String`
  `toString(boolean verbose)`
  `void`
  `update()`
  Call notify() method on all observers.

  ### Methods inherited from class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

  ### Methods inherited from interface Iterable

  `forEach, spliterator`

- ## Constructor Details

  - ### InstructionList

    public InstructionList()
    Create (empty) instruction list.

  - ### InstructionList

    public InstructionList(BranchInstruction i)
    Create instruction list containing one instruction.
    Parameters:
      `i` - initial instruction

  - ### InstructionList

    public InstructionList(byte[] code)
    Initialize instruction list from byte array.
    Parameters:
      `code` - byte array containing the instructions

  - ### InstructionList

    public InstructionList(CompoundInstruction c)
    Initialize list with (nonnull) compound instruction. Consumes argument list, i.e., it becomes empty.
    Parameters:
      `c` - compound instruction (list)

  - ### InstructionList

    public InstructionList(Instruction i)
    Create instruction list containing one instruction.
    Parameters:
      `i` - initial instruction

- ## Method Details

  - ### findHandle

    public static InstructionHandle findHandle(InstructionHandle[] ihs, int[] pos, int count, int target)
    Find the target instruction (handle) that corresponds to the given target position (byte code offset).
    Parameters:
      `ihs` - array of instruction handles, i.e. il.getInstructionHandles()
      `pos` - array of positions corresponding to ihs, i.e. il.getInstructionPositions()
      `count` - length of arrays
      `target` - target position to search for
    Returns:
      target position's instruction handle if available

  - ### addObserver

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

  - ### append

    public BranchHandle append(BranchInstruction i)
    Append a branch instruction to the end of this list.
    Parameters:
      `i` - branch instruction to append
    Returns:
      branch instruction handle of the appended instruction

  - ### append

    public InstructionHandle append(CompoundInstruction c)
    Append a compound instruction.
    Parameters:
      `c` - The composite instruction (containing an InstructionList)
    Returns:
      instruction handle of the first appended instruction

  - ### append

    public InstructionHandle append(Instruction i)
    Append an instruction to the end of this list.
    Parameters:
      `i` - instruction to append
    Returns:
      instruction handle of the appended instruction

  - ### append

    public InstructionHandle append(Instruction i, CompoundInstruction c)
    Append a compound instruction, after instruction i.
    Parameters:
      `i` - Instruction in list
      `c` - The composite instruction (containing an InstructionList)
    Returns:
      instruction handle of the first appended instruction

  - ### append

    public InstructionHandle append(Instruction i, Instruction j)
    Append a single instruction j after another instruction i, which must be in this list of course!
    Parameters:
      `i` - Instruction in list
      `j` - Instruction to append after i in list
    Returns:
      instruction handle of the first appended instruction

  - ### append

    public InstructionHandle append(Instruction i, InstructionList il)
    Append another list after instruction i contained in this list. Consumes argument list, i.e., it becomes empty.
    Parameters:
      `i` - where to append the instruction list
      `il` - Instruction list to append to this one
    Returns:
      instruction handle pointing to the first appended instruction

  - ### append

    public BranchHandle append(InstructionHandle ih, BranchInstruction i)
    Append an instruction after instruction (handle) ih contained in this list.
    Parameters:
      `ih` - where to append the instruction list
      `i` - Instruction to append
    Returns:
      instruction handle pointing to the first appended instruction

  - ### append

    public InstructionHandle append(InstructionHandle ih, CompoundInstruction c)
    Append a compound instruction.
    Parameters:
      `ih` - where to append the instruction list
      `c` - The composite instruction (containing an InstructionList)
    Returns:
      instruction handle of the first appended instruction

  - ### append

    public InstructionHandle append(InstructionHandle ih, Instruction i)
    Append an instruction after instruction (handle) ih contained in this list.
    Parameters:
      `ih` - where to append the instruction list
      `i` - Instruction to append
    Returns:
      instruction handle pointing to the first appended instruction

  - ### append

    public InstructionHandle append(InstructionHandle ih, InstructionList il)
    Append another list after instruction (handle) ih contained in this list. Consumes argument list, i.e., it becomes empty.
    Parameters:
      `ih` - where to append the instruction list
      `il` - Instruction list to append to this one
    Returns:
      instruction handle pointing to the first appended instruction

  - ### append

    public InstructionHandle append(InstructionList il)
    Append another list to this one. Consumes argument list, i.e., it becomes empty.
    Parameters:
      `il` - list to append to end of this list
    Returns:
      instruction handle of the first appended instruction

  - ### contains

    public boolean contains(Instruction i)

  - ### contains

    public boolean contains(InstructionHandle i)

  - ### copy

    public InstructionList copy()
    Returns:
      complete, i.e., deep copy of this list

  - ### delete

    public void delete(Instruction i) throws TargetLostException
    Remove instruction from this list. The corresponding Instruction handles must not be reused!
    Parameters:
      `i` - instruction to remove
    Throws:
      `TargetLostException`

  - ### delete

    public void delete(Instruction from, Instruction to) throws TargetLostException
    Remove instructions from instruction 'from' to instruction 'to' contained in this list. The user must ensure that 'from' is an instruction before 'to', or risk havoc. The corresponding Instruction handles must not be reused!
    Parameters:
      `from` - where to start deleting (inclusive)
      `to` - where to end deleting (inclusive)
    Throws:
      `TargetLostException`

  - ### delete

    public void delete(InstructionHandle ih) throws TargetLostException
    Remove instruction from this list. The corresponding Instruction handles must not be reused!
    Parameters:
      `ih` - instruction (handle) to remove
    Throws:
      `TargetLostException`

  - ### delete

    public void delete(InstructionHandle from, InstructionHandle to) throws TargetLostException
    Remove instructions from instruction 'from' to instruction 'to' contained in this list. The user must ensure that 'from' is an instruction before 'to', or risk havoc. The corresponding Instruction handles must not be reused!
    Parameters:
      `from` - where to start deleting (inclusive)
      `to` - where to end deleting (inclusive)
    Throws:
      `TargetLostException`

  - ### dispose

    public void dispose()
    Delete contents of list. Provides better memory utilization, because the system then may reuse the instruction handles. This method is typically called right after `MethodGen.getMethod()`.

  - ### findHandle

    public InstructionHandle findHandle(int pos)
    Gets instruction handle for instruction at byte code position pos. This only works properly, if the list is freshly initialized from a byte array or setPositions() has been called before this method.
    Parameters:
      `pos` - byte code position to search for
    Returns:
      target position's instruction handle if available

  - ### getByteCode

    public byte[] getByteCode()
    When everything is finished, use this method to convert the instruction list into an array of bytes.
    Returns:
      the byte code ready to be dumped

  - ### getEnd

    public InstructionHandle getEnd()
    Returns:
      end of list

  - ### getInstructionHandles

    public InstructionHandle[] getInstructionHandles()
    Returns:
      array containing all instructions (handles)

  - ### getInstructionPositions

    public int[] getInstructionPositions()
    Gets positions (offsets) of all instructions in the list. This relies on that the list has been freshly created from an byte code array, or that setPositions() has been called. Otherwise this may be inaccurate.
    Returns:
      array containing all instruction's offset in byte code

  - ### getInstructions

    public Instruction[] getInstructions()
    Returns:
      an array of instructions without target information for branch instructions.

  - ### getLength

    public int getLength()
    Returns:
      length of list (Number of instructions, not bytes)

  - ### getStart

    public InstructionHandle getStart()
    Returns:
      start of list

  - ### insert

    public BranchHandle insert(BranchInstruction i)
    Insert a branch instruction at start of this list.
    Parameters:
      `i` - branch instruction to insert
    Returns:
      branch instruction handle of the appended instruction

  - ### insert

    public InstructionHandle insert(CompoundInstruction c)
    Insert a compound instruction.
    Parameters:
      `c` - The composite instruction (containing an InstructionList)
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(Instruction i)
    Insert an instruction at start of this list.
    Parameters:
      `i` - instruction to insert
    Returns:
      instruction handle of the inserted instruction

  - ### insert

    public InstructionHandle insert(Instruction i, CompoundInstruction c)
    Insert a compound instruction before instruction i.
    Parameters:
      `i` - Instruction in list
      `c` - The composite instruction (containing an InstructionList)
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(Instruction i, Instruction j)
    Insert a single instruction j before another instruction i, which must be in this list of course!
    Parameters:
      `i` - Instruction in list
      `j` - Instruction to insert before i in list
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(Instruction i, InstructionList il)
    Insert another list before Instruction i contained in this list. Consumes argument list, i.e., it becomes empty.
    Parameters:
      `i` - where to append the instruction list
      `il` - Instruction list to insert
    Returns:
      instruction handle pointing to the first inserted instruction, i.e., il.getStart()

  - ### insert

    public BranchHandle insert(InstructionHandle ih, BranchInstruction i)
    Insert an instruction before instruction (handle) ih contained in this list.
    Parameters:
      `ih` - where to insert to the instruction list
      `i` - Instruction to insert
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(InstructionHandle ih, CompoundInstruction c)
    Insert a compound instruction.
    Parameters:
      `ih` - where to insert the instruction list
      `c` - The composite instruction (containing an InstructionList)
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(InstructionHandle ih, Instruction i)
    Insert an instruction before instruction (handle) ih contained in this list.
    Parameters:
      `ih` - where to insert to the instruction list
      `i` - Instruction to insert
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(InstructionHandle ih, InstructionList il)
    Insert another list before Instruction handle ih contained in this list. Consumes argument list, i.e., it becomes empty.
    Parameters:
      `ih` - where to append the instruction list
      `il` - Instruction list to insert
    Returns:
      instruction handle of the first inserted instruction

  - ### insert

    public InstructionHandle insert(InstructionList il)
    Insert another list.
    Parameters:
      `il` - list to insert before start of this list
    Returns:
      instruction handle of the first inserted instruction

  - ### isEmpty

    public boolean isEmpty()
    Tests for empty list.

  - ### iterator

    public Iterator<InstructionHandle> iterator()
    Specified by:
      `iterator` in interface `Iterable<InstructionHandle>`
    Returns:
      iterator that lists all instructions (handles)

  - ### move

    public void move(InstructionHandle ih, InstructionHandle target)
    Move a single instruction (handle) to a new location.
    Parameters:
      `ih` - moved instruction
      `target` - new location of moved instruction

  - ### move

    public void move(InstructionHandle start, InstructionHandle end, InstructionHandle target)
    Take all instructions (handles) from "start" to "end" and append them after the new location "target". Of course, "end" must be after "start" and target must not be located withing this range. If you want to move something to the start of the list use null as value for target.

    Any instruction targeters pointing to handles within the block, keep their targets.

    Parameters:
      `start` - of moved block
      `end` - of moved block
      `target` - of moved block

  - ### redirectBranches

    public void redirectBranches(InstructionHandle oldTarget, InstructionHandle newTarget)
    Redirect all references from oldTarget to newTarget, i.e., update targets of branch instructions.
    Parameters:
      `oldTarget` - the old target instruction handle
      `newTarget` - the new target instruction handle

  - ### redirectExceptionHandlers

    public void redirectExceptionHandlers(CodeExceptionGen[] exceptions, InstructionHandle oldTarget, InstructionHandle newTarget)
    Redirect all references of exception handlers from oldTarget to newTarget.
    Parameters:
      `exceptions` - array of exception handlers
      `oldTarget` - the old target instruction handle
      `newTarget` - the new target instruction handle
    See Also:
      - `MethodGen`

  - ### redirectLocalVariables

    public void redirectLocalVariables(LocalVariableGen[] lg, InstructionHandle oldTarget, InstructionHandle newTarget)
    Redirect all references of local variables from oldTarget to newTarget.
    Parameters:
      `lg` - array of local variables
      `oldTarget` - the old target instruction handle
      `newTarget` - the new target instruction handle
    See Also:
      - `MethodGen`

  - ### removeObserver

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

  - ### replaceConstantPool

    public void replaceConstantPool(ConstantPoolGen oldCp, ConstantPoolGen newCp)
    Replace all references to the old constant pool with references to the new constant pool

  - ### setPositions

    public void setPositions()

  - ### setPositions

    public void setPositions(boolean check)
    Give all instructions their position number (offset in byte stream), i.e., make the list ready to be dumped.
    Parameters:
      `check` - Perform sanity checks, for example if all targeted instructions really belong to this list

  - ### size

    public int size()
    Returns:
      length of list (Number of instructions, not bytes)

  - ### toString

    public String toString()
    Overrides:
      `toString` in class `Object`

  - ### toString

    public String toString(boolean verbose)
    Parameters:
      `verbose` - toggle output format
    Returns:
      String containing all instructions in this list.

  - ### 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.