标签：sleep return ble system.in catch 递归 输入 setname 示例
1、不使用循环，等比数列输出整型 n、2n、4n、8n……当大于max时，反向输出8n、4n、2n、n。
例如 n=10，max=100。 输出：
10
20
40
80
80
40
20
10
解题思路： 递归实现。
public class Test { public static void main(String[] args) { multiply(10, 100); } public static void multiply(int n, int max) { if (n < max) { System.out.println(n); multiply(2 * n, max); System.out.println(n); } } }
如果需要输出大于100后的数，则代码如下：
public class Test { public static void main(String[] args) { multiply(10, 100,10); } public static void multiply(int n, int max,int min) { if (n < max) { System.out.println(n); multiply(2 * n, max, min); } else{ System.out.println(n); divide(n,min); } } public static void divide(int n, int min) { if (n >= min) { System.out.println(n); divide(n / 2, min); } } }
2、Comparator 排序。 对某些对象 collection 进行整体排序。排序时将此接口的实现传递给Collections.sort方法或者Arrays.sort方法排序。实现 o1.compareTo(o2) 方法。如果是升序排序：o1小于o2，返回-1（负数），相等返回0，o1大于o2，返回1（正数）；反之降序。
代码如下：
public class Supermarket{ private String name; private double distance; //距离 private boolean isBusiness; // 是否营业 private double money; // 营业额 public Supermarket(String name, double distance, boolean isBusiness, double money) { super(); this.name = name; this.distance = distance; this.isBusiness = isBusiness; this.money = money; } @Override public String toString() { return name + "\t" + distance + "\t" + (isBusiness ? "是" : "否") + "\t" + money + "\r\n"; } public String getName() { return name; } public void setName(String name) { this.name = name; } public double getDistance() { return distance; } public void setDistance(double distance) { this.distance = distance; } public boolean isBusiness() { return isBusiness; } public void setBusiness(boolean isBusiness) { this.isBusiness = isBusiness; } public double getMoney() { return money; } public void setMoney(double money) { this.money = money; } }
public class Menu { public static void main(String[] args) { List<Supermarket> list = new ArrayList<Supermarket>(); Supermarket s1 = new Supermarket("天天超市", 1.0, true, 5000); Supermarket s2 = new Supermarket("地地超市", 3.5, false, 2000); Supermarket s3 = new Supermarket("人人超市", 2.5, true, 6000); Supermarket s4 = new Supermarket("神神超市", 5.0, false, 1000); Supermarket s5 = new Supermarket("佛佛超市", 2.0, true, 3000); list.add(s1); list.add(s2); list.add(s3); list.add(s4); list.add(s5); // System.out.println(list); String choose =""; Scanner input = new Scanner(System.in); while(!"0".equals(choose)){ System.out.println("1、店名\t2、距离\t3、是否营业\t4、营业额\t0、退出"); System.out.println("请选择："); choose = input.next(); switch (choose) { case "1": Collections.sort(list,new Comparator<Supermarket>() { @Override public int compare(Supermarket o1, Supermarket o2) { return o1.getName().compareTo(o2.getName()); } }); for (Supermarket supermarket : list) { System.out.print(supermarket.toString()); } break; case "2": Collections.sort(list, new Comparator<Supermarket>() { @Override public int compare(Supermarket o1, Supermarket o2) { if(o1.getDistance()<o2.getDistance()) return -1; return 1; } }); for (Supermarket supermarket : list) { System.out.print(supermarket.toString()); } break; case "3": Collections.sort(list, new Comparator<Supermarket>() { @Override public int compare(Supermarket o1, Supermarket o2) { if(o1.isBusiness()) return -1; return 1; } }); for (Supermarket supermarket : list) { System.out.print(supermarket.toString()); } break; case "4": Collections.sort(list, new Comparator<Supermarket>() { @Override public int compare(Supermarket o1, Supermarket o2) { if(o1.getMoney()<o2.getMoney()) return -1; return 1; } }); for (Supermarket supermarket : list) { System.out.print(supermarket.toString()); } break; case "0": System.out.println("程序结束。"); break; default: System.out.println("你输入的有误，请重新输入！"); break; } } input.close(); } }
3、SimpleDateFormat 时间转换工具类。用来格式化时间日期。
示例：显示当前时间，格式为 格式为 2017年7月15日 上午9点42分23秒， 每5秒显示一次时间。
解题思路：创建线程，格式化日期。 代码如下：
public class Timer extends Thread { @Override public void run() { SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 a HH时mm分ss秒"); // a --> AM, PM try { while (true) { Date date = new Date(); //获取当前时间 String time = format.format(date); //格式化时间 System.out.println(time); Thread.sleep(5000); } } catch (InterruptedException e) { e.printStackTrace(); } } }
标签：sleep return ble system.in catch 递归 输入 setname 示例
原文地址：http://www.cnblogs.com/tawny-tw/p/7194016.html
