把起始格添加到 "开启列表"
do
{ 寻找开启列表中F值最低的格子, 我们称它为当前格. 把它切换到关闭列表. 对当前格相邻的8格中的每一个 if (它不可通过 || 已经在 "关闭列表" 中) { 什么也不做. } if (它不在开启列表中) { 把它添加进 "开启列表", 把当前格作为这一格的父节点, 计算这一格的 FGH }if (它已经在开启列表中) { if (用G值为参考检查新的路径是否更好, 更低的G值意味着更好的路径) { 把这一格的父节点改成当前格, 并且重新计算这一格的 GF 值. } }目标格已经在 "开启列表", 这时候路径被找到跳出循环；
} while(开启列表不为空)
如果开启列表已经空了,目标格没找到 说明路径不存在.
最后从目标格开始, 沿着每一格的父节点移动直到回到起始格, 这就是路径.

package com.darrenchan.graph;import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.util.Stack;public class AStarAlgorithm {private static final int[][] DIREC = {{-1, 0}, {-1, 1}, {0, 1}, {1, 1},{1, 0}, {1, -1}, {0, -1}, {-1, -1}};public static void main(String[] args) {Scanner scanner = new Scanner(System.in);System.out.println("please enter (rows cols x1 y1 x2 y2): ");final int rows = scanner.nextInt();final int cols = scanner.nextInt();int x1 = scanner.nextInt();int y1 = scanner.nextInt();int x2 = scanner.nextInt();int y2 = scanner.nextInt();scanner.close();// generate a two-dimension array filled with 0int map[][] = new int[rows][cols];for (int i = 0; i < rows; i++) {int tmp[] = new int[cols];Arrays.fill(tmp, 0);map[i] = tmp;}int midr = rows / 2;int midc = cols / 2;/*map[midr - 1][midc] = 1;map[midr][midc] = 1;map[midr + 1][midc] = 1;*/for (int i = 1; i < rows - 1; i++) {map[i][midc] = 1;}map[2][6] = 1;map[3][6] = 1;map[4][6] = 1;map[5][6] = 1;findPath(map, x1, y1, x2, y2);}private static void findPath(int[][] map, int x1, int y1, int x2, int y2) {List<Position> openList = new ArrayList<AStarAlgorithm.Position>();//起始列表List<Position> closeList = new ArrayList<AStarAlgorithm.Position>();//关闭列表boolean findFlag = false;Position termPos = null;// 起始点Position startPos = new Position(x1, y1, calcH(x1, y1, x2, y2));openList.add(startPos);//把起始点加入起始列表do {// 通过在开启列表中找到F值最小的点作为当前点Position currentPos = openList.get(0);for (int i = 0; i < openList.size(); i++) {if (currentPos.F > openList.get(i).F) {currentPos = openList.get(i);}}// 将找到的当前点放到关闭列表中，并从开启列表中删除
            closeList.add(currentPos);openList.remove(currentPos);//遍历当前点对应的8个相邻点for (int i = 0; i < DIREC.length; i++) {int tmpX = currentPos.row + DIREC[i][0];int tmpY = currentPos.col + DIREC[i][1];if (tmpX < 0 || tmpX >= map.length || tmpY < 0 || tmpY >= map[0].length) {continue;}//创建对应的点Position tmpPos = new Position(tmpX, tmpY, calcH(tmpX, tmpY, x2, y2), currentPos);//map中对应的格子中的值为1（障碍）， 或对应的点已经在关闭列表中if (map[tmpX][tmpY] == 1 || closeList.contains(tmpPos)) {continue;}//如果不在开启列表中，则加入到开启列表if (!openList.contains(tmpPos)) {openList.add(tmpPos);} else {// 如果已经存在开启列表中，则用G值考察新的路径是否更好，如果该路径更好，则把父节点改成当前格并从新计算FGHPosition prePos = null;for (Position pos : openList) {if (pos.row == tmpX && pos.col == tmpY) {prePos = pos;break;}}if (tmpPos.G < prePos.G) {prePos.setFaPos(currentPos);}}}// 判断终点是否在开启列表中for (Position tpos : openList) {if (tpos.row == x2 && tpos.col == y2) {termPos = tpos;findFlag = true;break;}}} while(openList.size() != 0);if(!findFlag) {System.out.println("no valid path!");return;}Stack<String> resStack = new Stack<String>();String pattern = "(%d, %d)";if (termPos != null) {resStack.push(String.format(pattern, termPos.row, termPos.col));while(termPos.fa != null) {termPos = termPos.fa;resStack.push(String.format(pattern, termPos.row, termPos.col));}}StringBuilder sb = new StringBuilder();while (!resStack.empty()) {sb.append(resStack.pop());if (!resStack.empty()) {sb.append(" -> ");}}System.out.println(sb.toString());}/*** 计算某个格子的H值* @param x* @param y* @param tx 终点的x值* @param ty 终点的y值* @return*/private static int calcH(int x, int y, int tx, int ty) {int diff = Math.abs(x - tx) + Math.abs(y - ty);return diff * 10;}static class Position {public int F;public int G;public int H;public Position fa;public int row;public int col;public Position() {}public Position(int row, int col, int H) {this(row, col, H, null);}public Position(int row, int col, int H, Position pos) {this.H = H;this.row = row;this.col = col;this.fa = pos;this.G = calcG();this.F = G + H;}/*** 计算某个点到起始点的代价G* @return*/private int calcG() {if (fa == null) return 0;if (fa.row != this.row && fa.col !=  this.col) {return 14 + fa.G;}return 10 + fa.G;}public void setFaPos(Position pos) {this.fa = pos;this.G = calcG();this.F = G + H;}@Overridepublic boolean equals(Object obj) {if (obj == null) {return false;}if (!(obj instanceof Position)) {return false;}Position pos = (Position) obj;return this.row == pos.row && this.col == pos.col;}@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + row;result = prime * result + col;return result;}}}