java基础 练习，通过入口函数随机一个N值，打印出一个相应的菱形

首先这个题目不难，思路也很清晰，画图即可。

其次实现到什么程度，如何提高代码可重用性，及可扩展性。下面这段代码实际相当于一个工具类了，用于画出菱形的形状，

菱形的形状可能菱形高度（随机数代替）是奇数或偶数，这里当高度为偶数时打印的菱形不算很严谨。由于比较懒不想手动在控制台输入一些数，于是采用随机数代替。

用Star类可以控制每一个输出的形状，虽然整体是一个菱形，但是可以自定义用任何符号(空格除外)拼图。

对了，方法多种，下列非最优解，欢迎探讨。

1、CreateStar 类，用于创建菱形

public class CreateStar {
 private static int xLength = 0 ; //行高度
 private static int yLength = 0 ; //列高度
 private static Map<  Integer ,List<Star> > map = new HashMap< Integer,List<Star> >(); // 存
 private int num = 0; //打印多少行
 private boolean odevity =  false ; //默认奇数
 private static class lazyHolder {
 private static final CreateStar INSTANCE = new CreateStar();
 }
 public static CreateStar me() {
 return getInstance();
 }
 public static CreateStar getInstance() {
 System.out.println(LogUtil.getLog());
 return lazyHolder.INSTANCE;
 }
 public CreateStar() {
 //
 System.out.println(LogUtil.getLog());
 }
 public CreateStar(int num) {
 System.out.println(LogUtil.getLog());
 this.num = num;
 this.odevity = num % 2 == 0 ? true : false;
 this.xLength = num % 2 != 0 ? num : (num-1);
 this.yLength = num;
 }
 public void setnum(int num) {
 System.out.println(LogUtil.getLog());
 this.num = num;
 }
 public Map<Integer,List<Star>> getStars() {
 System.out.println(LogUtil.getLog());
 if(yLength == 0 && num != 0) {
 new CreateStar(this.num);
 }
 int start = startIndex(xLength); // 起始点
 int invert; //反转偏移
 for ( int y =0; y < yLength; y ++ ) {
 List list = new ArrayList();
 int index = 0; //当前游标
 if(this.odevity) invert = 2*y >= xLength ? (xLength - y) : 0; //奇偶性决定反转游标偏移量
 else invert = 2*y >= xLength ? (xLength -1 - y) : 0;
 for( int x = 0; x < xLength; x++ ) {
 index ++;
 Star star = new Star();
 star.setId(UUID.randomUUID().toString().replaceAll("-"," "));
 if(2*y >= xLength) { //反转
 if( index >= (start - invert) && index <= (start + invert) ) {
 star.setCode(1);
 }else {
 star.setCode(0);
 }
 }else if( index >= (start - y) && index <= (start + y) ) {
 star.setCode(1);
 }else {
 star.setCode(0);
 }
 list.add(star);
 }
 map.put(y,list);
 }
 return map;
 }
 /**
 * 起始点坐标
 * @param width
 * @return
 */ private static int startIndex( int width ) {
 System.out.println(LogUtil.getLog());
 return width%2 ==0 ? width/2 : width/2+1;
 }
 public void printStarsMap (Map<Integer,List<Star>> map) {
 System.out.println(LogUtil.getLog());
 for (int h=0; h < (num == 0 ? map.size() : num); h++) {
 map.get(h).forEach( star -> System.out.print(star.getStar() ));
 System.out.println();
 }
 }
 public void printStarsMap (Map<Integer,List<Star>> map,String sign) {
 System.out.println(LogUtil.getLog());
 for (int h=0; h < (num == 0 ? map.size() : num); h++) {
 map.get(h).forEach( star -> System.out.print(star.getStar(sign) ));
 System.out.println();
 }
 }
 public void printStarsMap (String sign) {
 System.out.println(LogUtil.getLog());
 map = map.size()<=0 ? this.getStars() : map;
 for (int h=0; h < (num == 0 ? map.size() : num); h++) {
 map.get(h).forEach( star -> System.out.print(star.getStar(sign) ));
 System.out.println();
 }
 }
}
 

2、PrintStars 类，用于测试打印菱形

使用一些随机数，模拟用户想要的数据（不想自己手动输入）

public class PrintStars {
 private static int height = 0;
 public static void main(String[] args)throws Exception {
 System.out.println(LogUtil.getLog());
 height = Integer.parseInt( String.valueOf(new Date().getTime()).substring(11,12) ) ;
// CreateStar createStar = new CreateStar();
// createStar.setnum(height < 1 ? 1 : height);
// new PrintStars().printStarsMap(createStar.getStars());
 System.out.println(height);
 new CreateStar(StringUtil.random(20)).printStarsMap("&*");
 CreateStar.me().printStarsMap( new CreateStar(14).getStars() );
// CreateStar.newInstance().printStarsMap( new CreateStar(height < 1 ? 1 : height).getStars() );
 }
}
 

3、Star 类，打印格式，默认打印☆，可自定义

public class Star implements Serializable {
 private static final String STAR = "☆";
 private String id;
 // 0 空格 1 ☆
 private int code;
 public String getId() {
 return id;
 }
 public void setId(String id) {
 this.id = id;
 }
 public void setCode(int code) {
 this.code = code;
 }
 public String getStar () {
 return code == 0 ? " " : STAR ;
 }
 public String getStar (String star) {
 if( code == 0) {
 StringBuilder sb = new StringBuilder("");
 for (int i = 0; i < star.length(); i++) {
 sb.append(" ");
 }
 return sb.toString();
 }else {
 return star;
 }
 }
}
 

4、DateUtil，常用时间处理工具类

public class DateUtil {
 private static Random random = new Random();
 private static String pool = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM" ;
 /**
 * 根据系统时间随机获取一个编号
 * @param len
 * @return
 */ public static Long createNumber(int len){
 StringBuilder sb = new StringBuilder(getNow("yyyyMMddHHmmss"));
 for(int i = 0 ; i++<len ;){
 sb.append(random(10));
 }
 return Long.parseLong(sb.toString());
 }
 /**
 * 根据系统时间随机获取一个编号
 * @param len
 * @return
 */ public static String createCode(int len){
 StringBuilder sb = new StringBuilder(getNow("yyyyMMddHHmmss"));
 for(int i = 0 ; i++<len ;){
 sb.append( pool.charAt(random(pool.length()) ));
 }
 return sb.toString();
 }
 /**
 * 获取处理耗时
 * @param start
 * @param end
 * @return
 */ public static String getTimeConsuming( long start,long end){
 long time=end-start;//计算插入耗时
 return "耗时:t"+(time>10000?getTime(time, "mm分ss秒"):time+"毫秒");
 }
 /**
 * 获取当前系统时间
 * @param format 日期转化格式
 * 建议格式:yyyy-MM-dd HH:mm:ss
 * @return String 日期
 */ public static String getNow(String format){
 return new SimpleDateFormat(format).format(new Date());
 }
 public static String getNow(){
 return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
 }
 /**
 * 毫秒值转为 format类型的时间字符
 * @param time
 * @param format
 * @return
 */ public static String getTime(long time,String format){
 Calendar calendar=Calendar.getInstance();
 calendar.setTimeInMillis(time);
 return new SimpleDateFormat(format).format(calendar.getTime());
 }
 /**
 * 获取系统当前毫秒值
 * @return
 */ public static long getTime(){
 return System.currentTimeMillis();
 }
 /**
 * 获取时间
 *
 * @param str 字符串日期格式 2017-06-26 13:21:12
 * 统一解析格式 yyyy-MM-dd HH:mm:ss
 * @return date
 */ public static Date getDate(String str){
 String format="yyyy-MM-dd HH:mm:ss";
 SimpleDateFormat sdf=new SimpleDateFormat(format);
 Date date=null;
 try {
 date=sdf.parse(str);
 } catch (ParseException e) {
 e.printStackTrace();
 }
 return date;
 }
 /**
 * 获取随机数
 * @param ran
 * @return
 */ public static int random(int ran){
 return random.nextInt(ran == 0 ? 1 : ran );
 }
}
 

5.StringUtil

public class StringUtil extends DateUtil {
 private static final String POOL = "qwertyuiopasdfghjklzxcvbnm";
 /**
 * 获取字符串子串t在母串中的下标
 * @param s 母串
 * @param t 子串
 * @return 存在则返回第一次查到的下标 查不到则返回-1
 */ public static int getIndex(String s,String t){
 int length=t.length();
 char c=t.charAt(0);
 for(int i=0;i<s.length();){
 if(c==s.charAt(i)){
 for(int j=1;;j++){
 char sc=s.charAt(++i);
 char st=t.charAt(j);
 if(sc==st){
 if(j<length-1) continue;
 else return i-j;
 }else{
 i-=j-1;
 break;
 }
 }
 }else{
 i++;
 }
 }
 return -1;
 }
 public static boolean isBlank(String string) {
 return string == null ? false : string == "" ? false : true;
 }
 public static boolean isNotBlank(String string) {
 return !isBlank(string);
 }
 public static String createCode() {
 StringBuilder sb = new StringBuilder();
 for(int i = 0; i<random(Integer.parseInt(String.valueOf(System.currentTimeMillis()).substring(12,13))); i++) {
 sb.append( random(2)%2 == 0 ? POOL.charAt(random(POOL.length())) : String.valueOf(POOL.charAt(random(POOL.length()))).toUpperCase() );
 }
 return sb.toString();
 }
}
 

LogUtil 用于控制台打印日志

public class LogUtil {
 private static String className() {
 return Thread.currentThread().getStackTrace()[3].getClassName();
 }
 private static String methodName() {
 return Thread.currentThread().getStackTrace()[3].getMethodName();
 }
 /**
 *
 * @return
 */ public static String getLog() {
 return DateUtil.getNow()+"t==>t"+className()+":"+methodName();
 }
}
 

结果图