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贴一些演示简单API的代码

2010-09-27 21:00 447 查看
 

 

有部分使用不正确，不要模仿：

 

/**
 * enum
 */
package com;
 
/**
 * @author Administrator
 *
 */
public class EnumTest {
 
       enum Week {
              Mon, Tue, Wed, Thu, Fri, Sat, Sun
       }
 
       /**
        * @param args
        */
       public static void main(String[] args) {
              System.out.println(Week.valueOf("Mon"));
              //
              System.out.println(Week.Mon);
              System.out.println(Week.Sun);
 
              Week[] w = Week.values();
              for (Week we : w) {
                     System.out.println(we);
              }
 
              switch (Week.Sun) {
              case Mon:
                     System.out.println("1");
                     break;
              default:
                     System.out.println("default");
              }
 
              System.out.println(Week.Mon.compareTo(Week.Fri));
             
              System.out.println(Coffee.small);
              System.out.println(Coffee.small.getSize());
              Coffee[] coffee = Coffee.values();
              for(Coffee c: coffee) {
                     System.out.println(c);
                     System.out.println(c.getSize());
              }
             
              System.out.println(Week.valueOf("Mon1"));
       }
 
}
 
enum Coffee {
       small(8), middle(10), large(12);
 
       private int size;
 
       Coffee(int size) {
              this.size = size;
       }
 
       public int getSize() {
              return size;
       }
}
Exception in thread "main" java.lang.IllegalArgumentException: No enum const class com.EnumTest$Week.Mon1
    at java.lang.Enum.valueOf(Enum.java:196)
    at com.EnumTest$Week.valueOf(EnumTest.java:1)
    at com.EnumTest.main(EnumTest.java:48)
Mon
Mon
Sun
Mon
Tue
Wed
Thu
Fri
Sat
Sun
default
-4
small
8
small
8
middle
10
large
12
 
 

/**
 *
 */
package com;
 
/**
 * @author Administrator
 *
 */
public class ForTest {
 
       public static void main(String[] args) {
              for (int i = 0, j = 10; i < 10;) {
                     System.out.println(i + j);
                     i++;
              }
       }
 
}
10
11
12
 
 

/**
 *
 */
package com;
 
import java.util.ArrayList;
import java.util.List;
 
/**
 * @author Administrator
 *
 */
public class TestWildcards {
       public static void main(String[] args) {
              List<Integer> myList = new ArrayList<Integer>();
              Bar bar = new Bar();
              bar.doInsert(myList);
       }
}
 
class Bar {
       void doInsert(List<? extends Object> list) {
              list.contains(new Dog());
              // 说不清楚具体是什么  可添加多种对象而造成危险 比如 Cat Dog等。
              list.add(new Object);  // compile error
       }
}
 
class Bar2 {
       void doInsert(List<? super String> list) {
              list.contains(new Dog());
              // string is a ? 合理
              list.add("test");
       }
}
 

import java.util.Comparator;
import java.util.PriorityQueue;
 
/**
 *
 */
 
/**
 * @author Administrator
 *
 */
public class PriorityQueueTest {
 
       static class PQsort implements Comparator<Integer> { // inverse sort
              public int compare(Integer one, Integer two) {
                     return two - one; // unboxing
              }
       }
 
       public static void main(String[] args) {
              int[] ia = { 1, 5, 3, 7, 6, 9, 8 }; // unordered data
              PriorityQueue<Integer> pq1 = new PriorityQueue<Integer>(); // use
              // natural
              // order
 
              for (int x : ia)
                     // load queue
                     pq1.offer(x);
              for (int x : ia)
                     // review queue
                     System.out.print(pq1.poll() + " ");
              System.out.println("");
 
              PQsort pqs = new PQsort(); // get a Comparator
              PriorityQueue<Integer> pq2 = new PriorityQueue<Integer>(10, pqs); // use
              // Comparator
 
              for (int x : ia)
                     // load queue
                     pq2.offer(x);
              System.out.println("size " + pq2.size());
              System.out.println("peek " + pq2.peek());
              System.out.println("size " + pq2.size());
              System.out.println("poll " + pq2.poll());
              System.out.println("size " + pq2.size());
              for (int x : ia)
                     // review queue
                     System.out.print(pq2.poll() + " ");
       }
 
}
1 3 5 6 7 8 9
size 7
peek 9
size 7
poll 9
size 6
8 7 6 5 3 1 null
 
 

/**
 *
 */
package com;
 
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
 
/**
 * @author Administrator
 *
 */
public class CollectionsTest {
 
       /**
        * @param args
        */
       public static void main(String[] args) {
 
              List list = new ArrayList();
              list.add("a");
              list.add("b");
              list.add("c");
              list.add("a23");
             
              Collections.sort(list);
              int i = Collections.binarySearch(list, "a23");
              System.out.println(list);
             
              PQsort pq = new PQsort();
              Collections.sort(list,pq);
              int j = Collections.binarySearch(list, "a23");
              System.out.println(i);
              System.out.println(j);
             
              int m = Collections.binarySearch(list, "a23", pq);
              System.out.println(m);
             
              System.out.println(list);
       }
 
}
 class PQsort implements Comparator<String> { // inverse sort
       public int compare(String one, String two) {
              return two.compareTo(one); // unboxing
              //return one.compareTo(two); // unboxing
       }
}
[a, a23, b, c]
1
-1
2
[c, b, a23, a]
 
 
 

/**
 *
 */
package file;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Serializable;
 
/**
 * @author Administrator
 *
 */
public class FileTest implements Serializable {
 
       public static void main(String[] args) {
             
 
              String filePath = "d://test";
 
              File file = new File(filePath);
 
              file.mkdir();
 
              File fileName = new File("d://test//t.dat");
              try {
                     fileName.createNewFile();
              } catch (IOException e) {
                     e.printStackTrace();
              }
              // file.delete();
 
              System.out.println(file.getAbsolutePath());
 
              FileWriter fw = null;
              try {
                     fw = new FileWriter(fileName);
                     fw.append("this is a test. /n");
                     fw.append("this is another test. /n");
                     fw.flush();
              } catch (IOException e) {
                     e.printStackTrace();
              } finally {
                     try {
                            fw.close();
                     } catch (IOException e) {
                            e.printStackTrace();
                     }
              }
 
              try {
                     FileReader fr = new FileReader(fileName);
                     while (fr.ready()) {
                            char[] cbuf = new char[1024];
                            fr.read(cbuf, 0, 1024);
                            System.out.println(cbuf);
                     }
              } catch (FileNotFoundException e) {
                     e.printStackTrace();
              } catch (IOException e) {
                     e.printStackTrace();
              }
 
              FileReader fr2 = null;
              try {
                     fr2 = new FileReader(fileName);
                     BufferedReader br = new BufferedReader(fr2);
                     while (br.ready()) {
                            System.out.println(br.readLine());
                     }
              } catch (FileNotFoundException e) {
                     e.printStackTrace();
              } catch (IOException e) {
                     e.printStackTrace();
              }
 
              try {
                     FileInputStream fis = new FileInputStream(fileName);
                     byte[] b = new byte[1023];
                     int num = 0;
                     while ((num = fis.available()) != 0) {
                            System.out.println("num: " + num);
                            fis.read(b, 0, num);
                            System.out.println(b);
                     }
              } catch (FileNotFoundException e) {
                     e.printStackTrace();
              } catch (IOException e) {
                     e.printStackTrace();
              }
 
       }
}
d:/test
this is a test.
this is another test.
 
this is a test.
this is another test.
num: 40
[B@f72617
 
 
 
 

/**
 *
 */
package com;
 
/**
 * @author Administrator
 *
 */
import java.util.regex.*;
 
class Regex2 {
       public static void main(String[] args) {
              Pattern p = Pattern.compile("//d?");
              Matcher m = p.matcher("23");
              boolean b = false;
 
              while (b = m.find()) {
                     System.out.print(m.start() + m.group() + m.end());          
              }
             
              System.out.println("/n");
           Matcher m2 = Pattern.compile("ab").matcher("cabcd");
              boolean b2 = false;
 
              while (b2 = m2.find()) {
                     System.out.print(m2.start() + m2.group() + m2.end());            
              }
       }
}
02113222
 
1ab3
 
 
 
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标签：  api string class list integer file
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