JAVA-day08 上午-集合零散知识、集合实现贪吃蛇

/*工具类：ArraysCollections*/import java.util.*;class Demo1 {public static void main(String[] args) {int[] arr ={34,56,12,6};//数组中的内容转成字符串System.out.println(Arrays.toString(arr));        //数组转成集合String[] arr2 = {"woeirui","eioruti","lfjgkldfg"};List<String> list = Arrays.asList(arr2);sop(list.size());sop(list);        //因为数组的长度是固定的，所以不能对集合进行添加，删除，修改//list.add("hello");//UnsupportedOperationException//sop(list);//数组转集合有什么用？可以利用集合的方法，因为集合的方法多list.contains("hello");Iterator<String> ite = list.iterator();while(ite.hasNext()){sop(ite.next());}int[] b = {3,4,5,6};List  list2 = Arrays.asList(b);sop(list2.size());///因为集合中存储的是引用类型的对象，所以把整个int类型的数组看成一个对象存到集合中，所以长度是1}public static void sop(Object obj){System.out.println(obj);}}

import java.util.*;class Demo2 {public static void main(String[] args) {List<String> list = new ArrayList<String>();list.add("oewuro");list.add("dfhfgh");list.add("yuiyuiyuiyui");list.add("qweqweqewqeqweqwe");        //数组长度最好是和集合中的对象个数相同String[] arr = list.toArray(new String[list.size()]);sop(arr.length);//为什么集合转数组？数组的长度是固定的，可以限制增删操作}public static void sop(Object obj){System.out.println(obj);}}

//Collectionsimport java.util.*;class CompareByLength implements Comparator<String>{public int compare(String str1,String str2){return str1.length()-str2.length();}}class  Demo3{public static void main(String[] args) {//对象可以重复，还想排序        List<String> list = new ArrayList<String>();list.add("oewuro");list.add("dfhfgh");list.add("yuiyuiyuiyui");list.add("qweqweqewqeqweqwe"); //Collections.sort(list);        //返回一个和默认排序规则相反的比较器Collections.reverseOrder()Collections.sort(list,Collections.reverseOrder());//使用指定的比较器排序//Collections.sort(list,new CompareByLength());//Collections.sort(list,Collections.reverseOrder(new CompareByLength()));sop(list);//将集合中的对象倒序//Collections.reverse(list);//sop(list);//获取集合中的最值//String str = Collections.max(list);//String str = getMax(list);//sop(str);}//实现获取集合中的最大值public static   <E extends Object & Comparable<? super E>>  E getMax(Collection<? extends E> col){Iterator<? extends E>  ite = col.iterator();            //得到集合中的第一个对象E obj = ite.next();while(ite.hasNext())    {    E object = ite.next();                int num = obj.compareTo(object);if(num<0)                   obj = object;}return obj;}public static void sop(Object obj){System.out.println(obj);}}

/*增强的for循环：不能操作下标，所以在使用数组时通常使用传统的for循环for(数据类型  变量名：被遍历的Collection集合或数组){}*/import java.util.*;class  Demo4{public static void main(String[] args) {int[] arr = {23,45,5,1,2,34};for(int num:arr)//foreach{sop(num);}        List<String> list = new ArrayList<String>();list.add("oewuro");list.add("dfhfgh");list.add("yuiyuiyuiyui");list.add("qweqweqewqeqweqwe"); for(String ss:list){sop(ss.toUpperCase());}HashMap<String,String>  map = new HashMap<String,String>();map.put("001","lisi");map.put("002","zhaosi");map.put("003","liuneng");for(String key:map.keySet()){String value = map.get(key);sop(key+"="+value);}for(Map.Entry<String,String> en:map.entrySet()){String key = en.getKey();String value  = en.getValue();sop(key+"="+value);}}public static void sop(Object obj){System.out.println(obj);}}

/*可变参数：必须定义在参数列表的最后*/class  Demo5{public static void main(String[] args) {//int[] arr={34,4,5,6,7,78};int sum = add2("owieurio",2,3,4,5,6,7,78,89,9,9,);sop(sum);}    //使用可变参数public static int add2(String ss,int... arr)//把接收到的数据封装到数组中{    int sum =0;for(int i=0;i<arr.length;i++){  sum = sum+arr[i];}return sum;}    public static int add(int[] arr){int sum =0;for(int i=0;i<arr.length;i++){  sum = sum+arr[i];}        return sum;}public static int add(int a,int b){return a+b;}public static int add(int a,int b,int c){return a+b+c;}public static void sop(Object obj){System.out.println(obj);}}

//静态导入import java.util.*;import static java.util.Arrays.*;class Demo6 {public static void main(String[] args) {int[] arr = {34,23,56,78,9};java.util.Arrays.sort(arr);//类名相同了，包名不能省略binarySearch(arr,78);System.out.println(Arrays.toString(arr));//方法名相同了，类名不能省略}}class Arrays{}

import java.util.*;class Demo7 {public static void main(String[] args) {//得到系统属性，存储到Properties集合中Properties  pro = System.getProperties();sop(pro);        Set<String> keys = pro.stringPropertyNames();for(String key:keys){String value = pro.getProperty(key);//根据键获取值sop(key+"="+value);}pro.setProperty("user.language","USA");Set<String> keys2 = pro.stringPropertyNames();for(String key:keys2){String value = pro.getProperty(key);//根据键获取值sop(key+"="+value);}}public static void sop(Object obj){System.out.println(obj);}}

//每个程序在运行时都有一个运行时类对象import java.io.*;class  Demo8{public static void main(String[] args) throws IOException{Runtime  runtime = Runtime.getRuntime();runtime.exec("notepad C:\\Users\\qq\\Desktop\\day03.txt");}}

集合实现贪吃蛇

class Node{private int i;private int j;public Node(){}public Node(int i,int j){   super();this.i = i;this.j = j;}public int hashCode(){return (i<<16)|j;}    public boolean equals(Object obj){if(obj == null)return false;if(obj == this)return true;if(obj instanceof Node){Node node =(Node)obj;return this.i==node.i && this.j ==node.j;}return false;}public void setI(int i){this.i = i;}public void setJ(int j){this.j = j;}public int getI(){return this.i;}public int getJ(){return this.j;}public String toString(){return "["+i+","+j+"]";}}

import java.util.*;class WormPanel{  //蛇   private Worm   worm;   //食物，用set存储   private Set<Node>  foods = new HashSet<Node>();   //行数   private int rows = 10;   //列数   private int cols = 32;   public WormPanel(){worm = new Worm();initFood(5);    }   public Worm  getWorm(){return this.worm;    }   //打印界面功能    public void print(){       for(int i=0;i<rows;i++){for(int j=0;j<cols;j++){    if(i==0 || i==rows-1)System.out.print("-");else if(j==0 || j==cols-1)System.out.print("|");else if(worm.contains(i,j))System.out.print("#");else if(foods.contains(new Node(i,j)))System.out.print("0");elseSystem.out.print(" ");}System.out.println();    }    }   //生成食物的方法    public void initFood(int count){        //随机生成食物的坐标        Random r = new Random();while(true){     int i = r.nextInt(rows-2)+1; int j = r.nextInt(cols-2)+1;              Node node =  new Node(i,j); if(worm.contains(i,j)) {    continue; }             foods.add(node);//不能添加重复坐标             if(foods.size()==count)                break;}    }   public  class Worm   {   //存储构成蛇的坐标的集合   private LinkedList<Node> nodes = new LinkedList<Node>();       //方向   private int direction;   public static final  int UP = -10;   public static final  int DOWN = 10;   public static final  int LEFT = -1;   public static final  int RIGHT = 1;   public Worm()   {  nodes.add(new Node(3,9));  nodes.add(new Node(4,9));  nodes.add(new Node(5,9));  nodes.add(new Node(5,10));  nodes.add(new Node(5,11));  nodes.add(new Node(6,11));  nodes.add(new Node(7,11));  this.direction = RIGHT;//默认向右走   }   //向前走一步   public void step()   {//先得到头结点Node head = nodes.getFirst();int i = head.getI()+direction/10;    int j = head.getJ()+direction%10;            //加入到头部的新结点head = new Node(i,j);nodes.addFirst(head);            //如果从食物集合中删除食物结点成功，说明遇到了食物if(foods.remove(head))    {   return;}            //删除蛇的尾部结点nodes.removeLast();   }   public void step(int direction)   {  if(this.direction+direction==0)  throw new RuntimeException("不能掉头");  this.direction = direction;  step();   }   //判断是否包含某个坐标的方法   public boolean contains(int i,int j)   {      return nodes.contains(new Node(i,j));   }   }}

import java.util.Scanner;class WormTest {public static void main(String[] args) {WormPanel  panel = new WormPanel();WormPanel.Worm  worm = panel.getWorm();Scanner sc = new Scanner(System.in);while(true){   panel.print();   String str = sc.nextLine();   if("u".equalsIgnoreCase(str))               worm.step(WormPanel.Worm.UP);   else if("d".equalsIgnoreCase(str))               worm.step(WormPanel.Worm.DOWN);   else if("l".equalsIgnoreCase(str))               worm.step(WormPanel.Worm.LEFT);   else if("r".equalsIgnoreCase(str))               worm.step(WormPanel.Worm.RIGHT);   else if("q".equalsIgnoreCase(str)){               System.out.println("baibai");   break;}   else   worm.step();}}}