Two sided (bidirectional) list in Java
Is there something like a two sided list in Java? Maybe a third party implementation?
Here a little example to demonstrate what I have in mind.
Original state:
A: 0-1-2-3 | | | | B: 0-1-2-3
After removal of element 1 in B:
Null | A: 0-1-2-3 | / / B: 0-1-2
The data structure must be accessib开发者_Python百科le from both sides. So it's more a mix of a bidirectional map and a list.
Things I thought about: a) Using two lists that store Integer objects. The downside is that those must always be kept in sync. b) Using a BidiMap from Apache Commons. The downside hereby is that it is unsorted and doesn't behave like a list when elements are removed (updating the other indidces).
Google has a bi-directional map.
At the end I used two lists that save the positions viewed from each site. As I always only modify one of the lists, the other will be recalculated. Below the full code (if someone is interested). It is embedded into a JFace document class, but the logic could also be implemented somewhere else.
public class AdaptedDocument extends AbstractDocument implements IDocumentListener {
private IDocument masterDocument;
private List<Integer> masterToSlaveMapping;
private List<Integer> slaveToMasterMapping;
private boolean setMaster = true;
private boolean replaceMaster = true;
public AdaptedDocument(IDocument masterDocument) {
super();
this.masterDocument = masterDocument;
masterDocument.addDocumentListener(this);
setTextStore(new CopyOnWriteTextStore(new GapTextStore()));
setLineTracker(new DefaultLineTracker());
getStore().set(masterDocument.get());
getTracker().set(masterDocument.get());
initializeMappings();
completeInitialization();
}
private void initializeMappings() {
masterToSlaveMapping = new ArrayList<Integer>();
slaveToMasterMapping = new ArrayList<Integer>();
for (int i=0; i<masterDocument.getLength(); i++) {
masterToSlaveMapping.add(i);
slaveToMasterMapping.add(i);
}
}
@Override
public void replace(int pos, int length, String text) throws BadLocationException {
if (replaceMaster) {
masterDocument.replace(pos, length, text);
}
super.replace(pos, length, text);
}
@Override
public void replace(int pos, int length, String text, long modificationStamp) throws BadLocationException {
if (replaceMaster) {
masterDocument.replace(pos, length, text);
}
super.replace(pos, length, text, modificationStamp);
}
@Override
public void set(String text) {
if (setMaster) {
masterDocument.set(text);
}
super.set(text);
}
@Override
public void set(String text, long modificationStamp) {
if (setMaster) {
if (masterDocument instanceof AbstractDocument) {
((AbstractDocument) masterDocument).set(text, modificationStamp);
}
else {
masterDocument.set(text);
}
}
super.set(text, modificationStamp);
}
public IDocument getMasterDocument() {
return this.masterDocument;
}
public void removeTextFromSlave(int offset, int length) throws BadLocationException {
if (length == 0) {
return;
}
try {
replaceSlaveOnly(offset, length, "");
for (int i=0; i<length; i++) {
slaveToMasterMapping.remove(offset);
}
}
catch (Exception e) {
throw new BadLocationException();
}
rebuildMasterToSlaveMapping();
}
public void addTextToSlaveOnly(int offset, String text) throws BadLocationException {
try {
replaceSlaveOnly(offset, 0, text);
for (int i=0; i<text.length(); i++) {
slaveToMasterMapping.add(offset + i, -1);
}
}
catch (Exception e) {
throw new BadLocationException();
}
rebuildMasterToSlaveMapping();
}
public void removeMasterDocumentRange(int offset, int length) throws BadLocationException {
if (length == 0) {
return;
}
StringBuffer buffer = new StringBuffer(get());
try {
int counter = 0;
for (int i=0; i<length; i++) {
int slaveOffset = masterToSlaveMapping.get(offset+i);
if (slaveOffset != -1) {
buffer.deleteCharAt(slaveOffset - counter);
slaveToMasterMapping.remove(slaveOffset - counter);
counter++;
}
}
}
catch (Exception e) {
throw new BadLocationException();
}
setSlaveOnly(buffer.toString());
rebuildMasterToSlaveMapping();
}
public void addMasterDocumentRange(int offset, int length) throws BadLocationException {
if (length == 0) {
return;
}
StringBuffer buffer = new StringBuffer(get());
String masterString = masterDocument.get();
try {
int counter = 0;
for (int i=0; i<length; i++) {
int slaveOffset = masterToSlaveMapping.get(offset+i);
if (slaveOffset == -1) {
int insertIndex = 0;
for (int j=offset+i; j>=0; j--) {
if (masterToSlaveMapping.get(j) != -1) {
insertIndex = masterToSlaveMapping.get(j)+1;
break;
}
}
buffer.insert(insertIndex + counter, masterString.charAt(offset + i));
slaveToMasterMapping.add(insertIndex + counter, offset+i);
counter++;
}
}
}
catch (Exception e) {
throw new BadLocationException();
}
setSlaveOnly(buffer.toString());
rebuildMasterToSlaveMapping();
}
public int toMasterOffset(int offset) throws BadLocationException {
try {
return slaveToMasterMapping.get(offset);
}
catch (Exception e) {
throw new BadLocationException();
}
}
public int toSlaveOffset(int offset) throws BadLocationException {
try {
return masterToSlaveMapping.get(offset);
}
catch (Exception e) {
throw new BadLocationException();
}
}
public IRegion toMasterRegion(int offset, int length) throws BadLocationException {
try {
if (length == 0) {
throw new BadLocationException();
}
int[] master = new int[length];
for (int i=0; i<length; i++) {
master[i] = slaveToMasterMapping.get(offset+i);
if (i > 0) {
if (master[i] != (master[i-1] + 1)) {
throw new BadLocationException();
}
}
}
return new Region(master[0], master.length);
}
catch (Exception e) {
throw new BadLocationException();
}
}
public IRegion toSlaveRegion(int offset, int length) throws BadLocationException {
try {
if (length == 0) {
throw new BadLocationException();
}
int[] slave = new int[length];
for (int i=0; i<length; i++) {
slave[i] = masterToSlaveMapping.get(offset+i);
if (i > 0) {
if (slave[i] != (slave[i-1] + 1)) {
throw new BadLocationException();
}
}
}
return new Region(slave[0], slave.length);
}
catch (Exception e) {
throw new BadLocationException();
}
}
@Override
public void documentAboutToBeChanged(DocumentEvent event) {
}
@Override
public void documentChanged(DocumentEvent event) {
setSlaveOnly(masterDocument.get());
}
private void setSlaveOnly(String text) {
setMaster = false;
super.set(text);
setMaster = true;
}
private void replaceSlaveOnly(int pos, int length, String text) throws BadLocationException {
replaceMaster = false;
super.replace(pos, length, text);
replaceMaster = true;
}
private void rebuildMasterToSlaveMapping() {
int length = masterDocument.getLength();
masterToSlaveMapping.clear();
for (int i=0; i<length; i++) {
masterToSlaveMapping.add(-1);
}
for (int i=0; i<slaveToMasterMapping.size(); i++) {
int masterOffset = slaveToMasterMapping.get(i);
if (masterOffset != -1) {
masterToSlaveMapping.set(masterOffset, i);
}
}
}
}
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