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import java.util.*;
import java.text.SimpleDateFormat;
public class Repository {
private String name;
private Commit head;
private int size;
public Repository(String name) {
if (name == null || name.isEmpty()) {
throw new IllegalArgumentException("Repository needs a name!");
}
this.name = name;
}
public String getRepoHead() {
if (head == null) {
return null;
}
return head.id;
}
public int getRepoSize() {
Commit temp = head;
int size = 0;
while (temp != null) {
size++;
temp = temp.past;
}
this.size = size;
return size;
}
public String toString() {
if (head == null) {
return name + " - No commits";
}
return name + " - Current head: " + head.toString();
}
public boolean contains(String targetId) {
Commit temp = head;
while (temp != null) {
if (temp.id.equals(targetId)) {
return true;
}
temp = temp.past;
}
return false;
}
public String getHistory(int n) {
if (n <= 0) {
throw new IllegalArgumentException("do you want the history or not?");
}
Commit temp = head;
String history = "";
if (n > size) {
while (temp != null) {
history += temp.toString() + "\n";
temp = temp.past;
}
}
for (int i = 0; i < n && temp != null; i++) {
history += temp.toString() + "\n";
temp = temp.past;
}
return history;
}
public String commit(String message) {
if (head == null) {
head = new Commit(message);
return head.id;
}
Commit old = head;
head = new Commit(message, old);
size++;
return head.id;
}
public boolean drop(String targetId) {
// list is empty
if (head == null) {
return false;
}
size--;
Commit temp = head;
// front
if (temp.id.equals(targetId)) {
head = temp.past;
return true;
}
// middle
while (temp.past != null && temp.past.past != null) {
if (temp.past.id == targetId) {
temp.past = temp.past.past;
return true;
}
temp = temp.past;
}
// end
if (temp.past != null && temp.past.id.equals(targetId)) {
temp.past = null;
return true;
}
// if we get here, targetId was not found, return size to initial state
size++;
return false;
}
public void synchronize(Repository other) {
if (head == null && other.head == null) {
head = null;
} else if (head == null) {
head = other.head;
other.head = null;
} else if (other.head == null) {
other.head = null;
} else {
List<Commit> commitList = new ArrayList<>();
Comparator commitComparator = new Comparator<Commit>() {
public int compare(Commit one, Commit two) {
return Long.compare(one.timeStamp, two.timeStamp);
}
};
Commit temp = head;
while (temp != null) {
commitList.add(temp);
temp = temp.past;
}
temp = other.head;
while (temp != null) {
commitList.add(temp);
temp = temp.past;
}
commitList.sort(commitComparator);
Commit prev = null;
for (Commit commit : commitList) {
commit.past = prev;
prev = commit;
}
head = commitList.get(commitList.size() - 1);
other.head = null;
}
}
/**
* DO NOT MODIFY
* A class that represents a single commit in the repository.
* Commits are characterized by an identifier, a commit message,
* and the time that the commit was made. A commit also stores
* a reference to the immediately previous commit if it exists.
*
* Staff Note: You may notice that the comments in this
* class openly mention the fields of the class. This is fine
* because the fields of the Commit class are public. In general,
* be careful about revealing implementation details!
*/
public class Commit {
private static int currentCommitID;
/**
* The time, in milliseconds, at which this commit was created.
*/
public final long timeStamp;
/**
* A unique identifier for this commit.
*/
public final String id;
/**
* A message describing the changes made in this commit.
*/
public final String message;
/**
* A reference to the previous commit, if it exists. Otherwise, null.
*/
public Commit past;
/**
* Constructs a commit object. The unique identifier and timestamp
* are automatically generated.
* @param message A message describing the changes made in this commit.
* @param past A reference to the commit made immediately before this
* commit.
*/
public Commit(String message, Commit past) {
this.id = "" + currentCommitID++;
this.message = message;
this.timeStamp = System.currentTimeMillis();
this.past = past;
}
/**
* Constructs a commit object with no previous commit. The unique
* identifier and timestamp are automatically generated.
* @param message A message describing the changes made in this commit.
*/
public Commit(String message) {
this(message, null);
}
/**
* Returns a string representation of this commit. The string
* representation consists of this commit's unique identifier,
* timestamp, and message, in the following form:
* "[identifier] at [timestamp]: [message]"
* @return The string representation of this collection.
*/
@Override
public String toString() {
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss z");
Date date = new Date(timeStamp);
return id + " at " + formatter.format(date) + ": " + message;
}
/**
* Resets the IDs of the commit nodes such that they reset to 0.
* Primarily for testing purposes.
*/
public static void resetIds() {
Commit.currentCommitID = 0;
}
}
}
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