I need help to implement the doubly LinkedList project:

package project;

import java.io.FileNotFoundException;

public enum Move

{

LEFT, RIGHT, UP, DOWN, DBL_LEFT, DBL_RIGHT, DBL_UP, DBL_DOWN

/** * This class represents a board configuration in the 8-puzzle. Only the initial configuration is * generated by a constructor, while intermediate configurations will be generated via calling * the method successorState(). State objects will form two circular doubly-linked lists OPEN and * CLOSED, which will be used by the A* algorithm to search for a path from a given initial board * configuration to the final board configuration below: * * 1 2 3 * 8 4 * 7 6 5 * * The final configuration (i.e., the goal state) above is not explicitly represented as an object * of the State class. */

public class State implements Cloneable, Comparable { public int[][] board; // configuration of tiles public State previous; // previous node on the OPEN/CLOSED list public State next; // next node on the OPEN/CLOSED list public State predecessor; // predecessor node on the path from the initial state public Move move; // the move that generated this state from its predecessor public int numMoves; // number of moves from the initial state to this state

public static Heuristic heu; // heuristic used. shared by all the states. private int numMismatchedTiles = -1; // number of mismatched tiles between this state // and the goal state; negative if not computed yet. private int ManhattanDistance = -1; // Manhattan distance between this state and the // goal state; negative if not computed yet. private int numSingleDoubleMoves = -1; // number of single and double moves with each double // move counted as one; negative if not computed yet.

/** * Constructor (for the initial state). * * It takes a 2-dimensional array representing an initial board configuration. The empty * square is represented by the number 0. * * a) Initialize all three links previous, next, and predecessor to null. * b) Set move to null and numMoves to zero. * * @param board * @throws IllegalArgumentException if board is not a 3X3 array or its nine entries are * not respectively the digits 0, 1, ..., 8. */ public State(int[][] board) throws IllegalArgumentException { // TODO } /** * Constructor (for the initial state) * * It takes a state from an input file that has three rows, each containing three digits * separated by exactly one blank. Every row starts with a digit. The nine digits are * from 0 to 8 with no duplicates. * * Do the same initializations as for the first constructor. * * @param inputFileName * @throws FileNotFoundException * @throws IllegalArgumentException if the file content does not meet the above requirements. */ public State (String inputFileName) throws FileNotFoundException, IllegalArgumentException { // TODO } /** * Generate the successor state resulting from a given move. Throw an exception if the move * cannot be executed. Besides setting the array board[][] properly, you also need to do the * following: * * a) set the predecessor of the successor state to this state; * b) set the private instance variable move of the successor state to the parameter m; * c) Set the links next and previous to null; * d) Set the variable numMoves for the successor state to this.numMoves + 1. * * @param m one of the moves LEFT, RIGHT, UP, DOWN, DBL_LEFT, DBL_RIGHT, DBL_UP, and DBL_DOWN * @return null if the successor state is this.predecessor * successor state otherwise * @throws IllegalArgumentException if LEFT when the empty square is in the right column, or * if RIGHT when the empty square is in the left column, or * if UP when the empty square is in the bottom row, or * if DOWN when the empty square is in the top row, or * if DBL_LEFT when the empty square is not in the left column, or * if DBL_RIGHT when the empty square is not in the right column, or * if DBL_UP when the empty square is not in the top row, or * if DBL_DOWN when the empty square is not in the bottom row. */ public State successorState(Move m) throws IllegalArgumentException { // TODO return null; } /** * Determines if the board configuration in this state can be rearranged into the goal configuration. * According to the PowerPoint notes that introduce the 8-puzzle, we check if this state has an odd number * of inversions. */ /** * * @return true if the puzzle starting in this state can be rearranged into the goal state. */ public boolean solvable() { // TODO return false; } /** * Check if this state is the goal state, namely, if the array board[][] stores the following contents: * * 1 2 3 * 8 0 4 * 7 6 5 * * @return */ public boolean isGoalState() { // TODO return false; } /** * Write the board configuration according to the following format: * * a) Output row by row in three lines with no indentations. * b) Two adjacent tiles in each row have exactly one blank in between. * c) The empty square is represented by a blank. * * For example, * * 2 3 * 1 8 4 * 7 6 5 * */ @Override public String toString() { // TODO return null; } /** * Create a clone of this State object by copying over the board[][]. Set the links previous, * next, and predecessor to null. * * The method is called by SuccessorState(); */ @Override public Object clone() { // TODO return null; }

/** * Compare this state with the argument state. Two states are equal if their arrays board[][] * have the same content. */ @Override public boolean equals(Object o) { // TODO return false; } /** * Evaluate the cost of this state as the sum of the number of moves from the initial state and * the estimated number of moves to the goal state using the heuristic stored in the instance * variable heu. * * If heu == TileMismatch, add up numMoves and the return values from computeNumMismatchedTiles(). * If heu == MahattanDist, add up numMoves and the return values of computeMahattanDistance(). * If heu == DoubleMoveHeuristic, add up numMoves and the return value of computeNumSingleDoubleMoves(). * * @return estimated number of moves from the initial state to the goal state via this state. * @throws IllegalArgumentException if heuristic is neither 0 nor 1. */ public int cost() throws IllegalArgumentException { // TODO return 0; }

/** * Compare two states by the cost. Let c1 and c2 be the costs of this state and the argument state s. * * @return -1 if c1 < c2 * 0 if c1 = c2 * 1 if c1 > c2 * * Call the method cost(). This comparison will be used in maintaining the OPEN list by the A* algorithm. */ @Override public int compareTo(State s) { // TODO return 0; }

/** * Return the value of the private variable numMismatchedTiles if it is non-negative, and compute its * value otherwise. * * @return the number of mismatched tiles between this state and the goal state. */ private int computeNumMismatchedTiles() { // TODO return 0; }

/** * Return the value of the private variable ManhattanDistance if it is non-negative, and compute its value * otherwise. * * @return the Manhattan distance between this state and the goal state. */ private int computeManhattanDistance() { // TODO return 0; } /** * Return the value of the private variable numSingleDoubleMoves if it is non-negative, and compute its value * otherwise. * * @return the value of the private variable numSingleDoubleMoves that bounds from below the number of moves, * single or double, which will take this state to the goal state. */ private int computeNumSingleDoubleMoves() { // TODO return 0; } }