贴一些演示简单API的代码

 

 

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