Java程序设计经典300例

一、基础篇(basic)

1.不借助第三者实现两个变量值的交换：

 1 package basic;
 2 
 3 import java.util.Scanner;
 4 
 5 public class ExchangeValue {
 6     public static void main(String[] args) {
 7         Scanner scan = new Scanner(System.in);
 8         System.out.println("请输入变量A的值：");
 9         long a = scan.nextLong();
10         System.out.println("请输入变量B的值：");
11         long b = scan.nextLong();
12         System.out.println("a=" + a + "\tb=" + b);
13         System.out.println("变量交换...\t");
14         a = a ^ b;
15         b = a ^ b;
16         a = a ^ b;
17         System.out.println("a=" + a + "\tb=" + b);
18     }
19 }

2.利用异或进行加解密：

 1 package basic;
 2 
 3 import java.util.Scanner;
 4 
 5 public class Encryption {
 6     public static void main(String[] args) {
 7         Scanner scan=new Scanner(System.in);
 8         System.out.println("请输入一个英文字符串或解密字符串");
 9         String password=scan.nextLine();
10         char[] array=password.toCharArray();
11         for(int i=0;i<array.length;++i){
12             array[i]=(char)(array[i]^20000);
13         }
14         System.out.println("加密或解密结果如下：");
15         System.out.println(new String(array));
16     }
17 }

3.利用BigDecimal求和：

 1 package basic;
 2 
 3 import java.math.BigDecimal;
 4 
 5 public class Factorial {
 6     public static void main(String[] args) {
 7         BigDecimal sum=new BigDecimal(0.0);
 8         BigDecimal factorial=new BigDecimal(1.0);
 9         int i=1;
10         while(i<=10){
11             sum=sum.add(factorial);
12             ++i;
13             factorial=factorial.multiply(new BigDecimal(1.0/i));
14         }
15         System.out.println("1+1/2!+1/3!+1/4!....+1/10!="+sum);
16     }
17 }

4.for循环打印空心菱形：

 1 package basic;
 2 
 3 public class Diamond {
 4     public static void main(String[] args) {
 5         printDiamond(6);
 6     }
 7 
 8     public static void printDiamond(int size) {
 9         if (size % 2 == 0) {
10             size++;
11         }
12         for (int i = 0; i < size / 2 + 1; ++i) {
13             for (int j = size / 2 + 1; j > i + 1; j--) {
14                 System.out.print(" ");
15             }
16             for (int j = 0; j < 2 * i + 1; j++) {
17                 if (j == 0 || j == 2 * i) {
18                     System.out.print("*");
19                 } else {
20                     System.out.print(" ");
21                 }
22             }
23             System.out.println("");
24         }
25         for (int i = size / 2 + 1; i < size; i++) {
26             for (int j = 0; j < i - size / 2; j++) {
27                 System.out.print(" ");
28             }
29             for (int j = 0; j < 2 * size - 1 - 2 * i; j++) {
30                 if (j == 0 || j == 2 * (size - i - 1)) {
31                     System.out.print("*");
32                 } else {
33                     System.out.print(" ");
34                 }
35             }
36             System.out.println("");
37         }
38     }
39 }

5.猴子分桃问题：一堆桃子，5个猴子先后到，每次都均分5份，扔掉多余的一个，拿走自己的那份。问最少有几个桃子，最后一个猴子得到几个桃子。

 1 package basic;
 2 
 3 public class MonkeyPeach {
 4     public static void main(String[] args) {
 5         int n = 1;
 6         int m = 0;
 7         int flag = 1;
 8         int monkeyNum = 5;
 9         while (true) {
10             flag = 1;
11             m = monkeyNum * n + 1;
12             for (int i = monkeyNum; i >= 1; i--) {
13                 if ((m % (monkeyNum - 1) == 0)) {
14                     m = m / (monkeyNum - 1) * monkeyNum + 1;
15                     flag++;
16                 } else {
17                     break;
18                 }
19             }
20             if (flag == monkeyNum)
21                 break;
22             n++;
23         }
24         System.out.println("桃子总数为:" + m);
25         System.out.println("第五个猴子得到的桃子数为:" + n);
26     }
27 }

6.约瑟夫问题：

 1 package basic;
 2 
 3 import javax.swing.JOptionPane;
 4 
 5 public class Josephus {
 6     public static void main(String[] args) {
 7         String s;
 8         int n, k, m, n1;
 9         s = JOptionPane.showInputDialog("请输入人数：");
10         n = Integer.parseInt(s);
11         n1 = n + 1;
12         s = JOptionPane.showInputDialog("请输入起始报数的人的编号：");
13         k = Integer.parseInt(s);
14         s = JOptionPane.showInputDialog("请输入死亡数字：");
15         m = Integer.parseInt(s);
16         int a[] = new int[n + 1];
17         a[0] = 0;
18         System.out.println("出局人的编号：");
19         for (int i = 1; i < a.length; i++) {
20             a[i] = 1;
21         }
22         for (int i = 1; i <= m; i++) {
23             if (n == 1)
24                 break;
25             else if (i == m) {
26                 n--;
27                 i = 0;
28                 a[k] = 0;
29                 System.out.print(k + " ");
30             }
31             do {
32                 k++;
33                 k = k % n1;
34             } while (a[k] != 1);
35         }
36         System.out.println("");
37         System.out.println("幸存者编号：" + k);
38     }
39 }

7.数独问题：

 1 package basic;
 2 
 3 import java.util.Scanner;
 4 
 5 public class Sudoku {
 6     public static void main(String[] args) {
 7         Scanner s = new Scanner(System.in);
 8         System.out.println("请输入要计算的数独维数(大于1的奇数):");
 9         int x = s.nextInt();
10         int h = 0;
11         int l = x / 2;
12         int[][] a = new int[x][x];
13         for (int i = 1; i <= x * x; i++) {
14             a[h][l] = i;
15             h--;
16             l++;
17             if (h < 0 && l >= x) {
18                 h += 2;
19                 l--;
20             } else if (h < 0) {
21                 h = x - 1;
22             } else if (l >= x) {
23                 l = 0;
24             } else if (a[h][l] > 0) {
25                 h += 2;
26                 l--;
27             }
28         }
29         for (int i = 0; i < x; i++) {
30             for (int j = 0; j < x; j++)
31                 System.out.print(a[i][j] + " ");
32             System.out.println();
33         }
34     }
35 }

8.数字格式转为货币字符串：

 1 package basic;
 2 
 3 import java.text.NumberFormat;
 4 import java.util.Locale;
 5 import java.util.Scanner;
 6 
 7 public class CurrencyFormat {
 8     public static void main(String[] args) {
 9         Scanner scan = new Scanner(System.in);
10         System.out.println("请输入一个货币数字：");
11         double number = scan.nextDouble();
12         NumberFormat format = NumberFormat.getCurrencyInstance(Locale.CHINA);
13         System.out.println("Locale.CHINA:" + format.format(number));
14         format = NumberFormat.getCurrencyInstance(Locale.US);
15         System.out.println("Locale.US:" + format.format(number));
16         format = NumberFormat.getCurrencyInstance(Locale.UK);
17         System.out.println("Locale.UK:" + format.format(number));
18     }
19 }

9.检验IP地址：

 1 package basic;
 2 
 3 import java.util.Scanner;
 4 
 5 public class IPAddress {
 6     public static void main(String[] args) {
 7         Scanner sc = new Scanner(System.in);
 8         System.out.println("请输入需要校验的IP地址：");
 9         String text = sc.nextLine();
10         String info = matches(text);
11         System.out.println(info);
12     }
13 
14     public static String matches(String text) {
15         if (text != null && !text.isEmpty()) {
16             String regex = "^(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|[1-9])\\."
17                     + "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)\\."
18                     + "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)\\."
19                     + "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)$";
20             if (text.matches(regex)) {
21                 return text + "是一个合法的IP地址！";
22             } else {
23                 return text + "不是一个合法的IP地址！";
24             }
25         }
26         return "请输入要验证的IP地址！";
27     }
28 }

10.检验电话号码：

 1 package basic;
 2 
 3 import java.util.Scanner;
 4 
 5 public class PhoneNumber {
 6     public static void main(String[] args) {
 7         Scanner sc = new Scanner(System.in);
 8         System.out.println("请输入电话号码:");
 9         String phoneNumber = sc.nextLine();
10         System.out.println(check(phoneNumber));
11     }
12 
13     public static String check(String phoneNumber) {
14         if (phoneNumber == null || phoneNumber.isEmpty())
15             return "请输入电话号码";
16         String regex = "^\\d{3}-?\\d{8}|\\d{4}-?\\d{8}$";
17         if (phoneNumber.matches(regex))
18             return phoneNumber + "是一个合法的电话号码！";
19         else
20             return phoneNumber + "不是一个合法的电话号码！";
21     }
22 }

11.字符串编码转换：

 1 package basic;
 2 
 3 import java.io.UnsupportedEncodingException;
 4 
 5 public class ChangeCharset {
 6     public static final String ISO_8859_1 = "ISO-8859-1";
 7 
 8     public static final String UTF_8 = "UTF-8";
 9 
10     public static final String GBK = "GBK";
11 
12     public static final String GB2312 = "GB2312";
13 
14     public String toISO_8859_1(String str) throws UnsupportedEncodingException {
15         return this.changeCharset(str, ISO_8859_1);
16     }
17 
18     public String toUTF_8(String str) throws UnsupportedEncodingException {
19         return this.changeCharset(str, UTF_8);
20     }
21 
22     public String toGBK(String str) throws UnsupportedEncodingException {
23         return this.changeCharset(str, GBK);
24     }
25 
26     public String toGB2312(String str) throws UnsupportedEncodingException {
27         return this.changeCharset(str, GB2312);
28     }
29 
30     public String changeCharset(String str, String newCharset)
31             throws UnsupportedEncodingException {
32         if (str != null) {
33             byte[] bs = str.getBytes();
34             return new String(bs, newCharset);
35         }
36         return null;
37     }
38 
39     public String changeCharset(String str, String oldCharset, String newCharset)
40             throws UnsupportedEncodingException {
41         if (str != null) {
42             byte[] bs = str.getBytes(oldCharset);
43             return new String(bs, newCharset);
44         }
45         return null;
46     }
47 
48     public static void main(String[] args) throws UnsupportedEncodingException {
49         ChangeCharset test = new ChangeCharset();
50         String str = "This is a 中文的 string";
51         System.out.println("str:" + str);
52         String iso8859_1 = test.toISO_8859_1(str);
53         System.out.println("转换为ISO-8859-1：" + iso8859_1);
54         String utf_8 = test.toUTF_8(str);
55         System.out.println("转换为UTF-8：" + utf_8);
56         String gbk = test.toGBK(str);
57         System.out.println("转换为GBK码：" + gbk);
58         String gb2312 = test.toGB2312(str);
59         System.out.println("转换为GB2312码：" + gb2312);
60     }
61 }

12.StringBuilder，StringBuffer和String的区别：

 1 package basic;
 2 
 3 public class BufferString {
 4     public static void main(String[] args) {
 5         String string = "";
 6         long startTime = System.nanoTime();
 7         for (int i = 20000; i < 50000; ++i)
 8             string += (char) i;
 9         long endTime = System.nanoTime();
10         System.out
11                 .println("String耗时：" + (endTime - startTime) / 1000000 + "ms");
12         StringBuffer stringBuffer = new StringBuffer();
13         startTime = System.nanoTime();
14         for (int i = 20000; i < 50000; ++i)
15             stringBuffer.append((char) i);
16         endTime = System.nanoTime();
17         System.out.println("StringBuffer耗时：" + (endTime - startTime) / 1000000
18                 + "ms");
19         StringBuilder stringBuilder = new StringBuilder();
20         startTime = System.nanoTime();
21         for (int i = 20000; i < 50000; ++i)
22             stringBuilder.append((char) i);
23         endTime = System.nanoTime();
24         System.out.println("StringBuilder耗时：" + (endTime - startTime) / 1000000
25                 + "ms");
26     }
27 }

13.利用TreeSet模拟数组：

 1 package basic;
 2 
 3 import java.util.Random;
 4 import java.util.TreeSet;
 5 
 6 public class NoRepeatRandom {
 7     public static void main(String[] args) {
 8         TreeSet<Integer> set = new TreeSet<Integer>();
 9         Random ran = new Random();
10         int count = 0;
11         while (count < 10) {
12             boolean succeed = set.add(ran.nextInt(100));
13             if (succeed)
14                 count++;
15         }
16         int size = set.size();
17         Integer[] array = new Integer[size];
18         set.toArray(array);
19         System.out.println("生成的随机不重复的数据如下：");
20         for (int value : array) {
21             System.out.print(value + "  ");
22         }
23     }
24 }

14.逆序遍历ArrayList：

 1 package basic;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 import java.util.ListIterator;
 6 
 7 public class ReverseOrder {
 8     public static void main(String[] args) {
 9         List<Integer> list = new ArrayList<Integer>();
10         for (int i = 0; i < 10; ++i)
11             list.add(i);
12         System.out.println("顺序输出：" + list);
13         System.out.print("逆序输出：");
14         ListIterator<Integer> li = list.listIterator();
15         for (li = list.listIterator(); li.hasNext();) {
16             li.next();
17         }
18         for (; li.hasPrevious();) {
19             System.out.print(li.previous() + "  ");
20         }
21     }
22 }

15.用LinkedList实现猴子大王问题：

 1 package basic;
 2 
 3 import java.util.Iterator;
 4 import java.util.LinkedList;
 5 
 6 public class Monkey {
 7     public static void main(String[] args) {
 8         LinkedList<Integer> monkeys = new LinkedList<Integer>();
 9         int number, cnt;
10         for (number = 1; number <= 100; ++number)
11             monkeys.addLast(number);
12         cnt = 100;
13         number = 0;
14         Iterator<Integer> it = monkeys.iterator();
15         while (cnt > 1) {
16             if (it.hasNext()) {
17                 it.next();
18                 ++number;
19             } else {
20                 it = monkeys.iterator();
21             }
22             if (number == 14) {
23                 number = 0;
24                 it.remove();
25                 --cnt;
26             }
27         }
28         System.out.println("猴子大王编号为：" + monkeys.element());
29     }
30 }

16.线程的启动和结束：

 1 package basic;
 2 
 3 import java.util.Date;
 4 
 5 class ThreadX implements Runnable {
 6     private Date runDate;
 7 
 8     @SuppressWarnings("deprecation")
 9     public void run() {
10         System.out.println("线程X已经启动...");
11         this.runDate = new Date();
12         System.out.println("启动时间：" + runDate.toLocaleString());
13     }
14 }
15 
16 class ThreadY extends Thread {
17     private boolean isRunState = false;
18 
19     public void start() {
20         this.isRunState = true;
21         super.start();
22     }
23 
24     public void run() {
25         int i = 0;
26         try {
27             while (isRunState) {
28                 this.setName("Thread-" + i++);
29                 System.out.println("线程Y" + this.getName() + "正在运行");
30                 Thread.sleep(200);
31             }
32         } catch (Exception e) {
33         }
34         System.out.println(this.getName() + "结束运行...");
35     }
36 
37     public void setRunning(boolean isRunState) {
38         this.isRunState = isRunState;
39     }
40 
41     public void startThreadY() {
42         System.out.println("启动线程Y...");
43         this.start();
44     }
45 
46     public void stopThreadY() {
47         System.out.println("结束线程Y...");
48         this.setRunning(false);
49     }
50 }
51 
52 public class StartThread {
53     public void startX() {
54         Runnable runnX = new ThreadX();
55         Thread threadX = new Thread(runnX);
56         threadX.start();
57     }
58 
59     public void startY() {
60         ThreadY ty = new ThreadY();
61         ty.startThreadY();
62         try {
63             Thread.sleep(1000);
64         } catch (Exception e) {
65             e.printStackTrace();
66         }
67         ty.stopThreadY();
68     }
69 
70     public static void main(String[] args) {
71         StartThread test = new StartThread();
72         test.startX();
73         test.startY();
74     }
75 }

17.设置线程优先级：

 1 package basic;
 2 
 3 class Clicker extends Thread {
 4     private int click = 0;
 5     private volatile boolean running = true;
 6 
 7     public int getClick() {
 8         return click;
 9     }
10 
11     public void run() {
12         while (running)
13             click += 1;
14     }
15 
16     public void normalStop() {
17         running = true;
18     }
19 }
20 
21 public class Pri {
22     public static void main(String[] args) {
23         Clicker trHigh, trLow;
24         trHigh = new Clicker();
25         trLow = new Clicker();
26         trHigh.setPriority(Thread.NORM_PRIORITY + 2);
27         trLow.setPriority(Thread.NORM_PRIORITY - 2);
28         trLow.start();
29         trHigh.start();
30         try {
31             Thread.sleep(1);
32         } catch (InterruptedException e) {
33         }
34         trHigh.normalStop();
35         trLow.normalStop();
36         try {
37             trHigh.join();
38             trLow.join();
39         } catch (InterruptedException e) {
40         }
41         System.out.println("trHigh的循环次数为：" + trHigh.getClick());
42         System.out.println("trLow的循环次数为：" + trLow.getClick());
43     }
44 }

posted @ 2015-05-15 20:50 XavierJZhang 阅读(2073) 评论(0) 编辑收藏举报

会员力量，点亮园子希望

刷新页面返回顶部

XavierJZhang

Java程序设计经典300例

公告