JAVA进阶20
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1、可视化日历程序（简陋版）
1 package cn.zh.abstrac; 2 3 import java.text.DateFormat; 4 import java.text.ParseException; 5 import java.text.SimpleDateFormat; 6 import java.util.Calendar; 7 import java.util.Date; 8 import java.util.GregorianCalendar; 9 import java.util.Scanner; 10 11 public class TestCalendar { 12 public static void main(String[] args) throws ParseException { 13 System.out.println("请输入一个日期：（格式：yyyy-MM-dd）"); 14 Scanner sc = new Scanner(System.in); 15 String str = sc.nextLine(); 16 DateFormat df = new SimpleDateFormat("yyyy-MM-dd"); 17 Date date = df.parse(str); 18 Calendar c = new GregorianCalendar(); 19 c.setTime(date); 20 21 int day = c.get(Calendar.DAY_OF_MONTH); 22 int days = c.getActualMaximum(Calendar.DATE); 23 System.out.println("日\\t一\\t二\\t三\\t四\\t五\\t六"); 24 25 c.set(Calendar.DAY_OF_MONTH, 1); 26 27 for (int i = 0; i < c.get(Calendar.DAY_OF_WEEK) - 1; i++) { 28 System.out.print ("\\t"); 29 } 30 31 for (int i = 1; i <= days; i++) { 32 if (day == c.get(Calendar.DAY_OF_MONTH)){ 33 System.out.print(c.get(Calendar.DAY_OF_MONTH) + "*\\t"); 34 }else { 35 System.out.print(c.get(Calendar.DAY_OF_MONTH) + "\\t"); 36 } 37 38 39 if (c.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) { 40 System.out.println(); //换行 41 } 42 c.add(Calendar.DAY_OF_MONTH, 1); 43 } 44 } 45 }
运行结果图
2、使用递归打印目录树结构
1 package cn.zh.abstrac; 2 3 import java.io.File; 4 5 public class TestFile { 6 public static void main(String[] args) { 7 File f = new File("E:\\\\小程序"); 8 printFile(f,0 ); 9 } 10 11 static void printFile(File file,int level) { 12 //输出层次 13 for (int i = 0; i < level; i++) { 14 System.out.print("-"); 15 } 16 System.out.println(file.getName()); 17 if (file.isDirectory()) { 18 File[] files = file.listFiles(); 19 20 for (File temp : files) { 21 printFile(temp,level+1); 22 } 23 } 24 25 } 26 }
运行结果图
3、枚举的用法
1 package cn.zh.abstrac; 2 3 import java.util.Random; 4 5 public class TestEnum { 6 public static void main(String[] args) { 7 //枚举遍历 8 for (week k : week.values()) { 9 System.out.println(k); 10 } 11 //switch语句中使用枚举 12 int a = new Random().nextInt(4); //生成0,1,2,3的随机数 13 switch (Season.values()[a]) { 14 case SPRING: 15 System.out.println("春天"); 16 break; 17 case SUMMER: 18 System.out.println("夏天"); 19 break; 20 case AUTUMN: 21 System.out.println("秋天"); 22 break; 23 case WINTER: 24 System.out.println("冬天"); 25 break; 26 } 27 } 28 } 29 enum Season{ 30 SPRING,SUMMER,AUTUMN,WINTER 31 } 32 enum week{ 33 星期一,星期二,星期三,星期四,星期五,星期六,星期日, 34 }
运行结果图
4、异常处理
1 package cn.zh.abstrac; 2 3 import java.io.FileNotFoundException; 4 import java.io.FileReader; 5 import java.io.IOException; 6 7 public class TestA { 8 public static void main(String[] args) { 9 FileReader reader = null; 10 try { 11 reader = new FileReader("d:/a.txt"); 12 System.out.println("111111111"); 13 char c = (char)reader.read(); 14 char c1 = (char)reader.read(); 15 System.out.println(""+c+c1); 16 }catch (FileNotFoundException e){ 17 System.out.println("2222222222222222"); 18 e.printStackTrace(); 19 }catch (IOException e){ 20 e.printStackTrace(); 21 }finally { 22 System.out.println("333333333333333333"); 23 try { 24 if(reader !=null){ 25 reader.close(); 26 } 27 } 28 catch (Exception e){ 29 e.printStackTrace(); 30 31 } 32 } 33 } 34 }
运行结果图
5、容器和数据结构
（1）简化版-手工实现ArrayList
1 package cn.zjc.mycollection; 2 3 public class SxtArrayList { 4 private Object[] elementDate; 5 private int size; 6 7 private static final int DEFALT_CAPACITY = 10; 8 9 public SxtArrayList() { 10 elementDate = new Object[DEFALT_CAPACITY]; 11 } 12 13 public SxtArrayList(int capacity) { 14 elementDate = new Object[capacity]; 15 } 16 17 public void add(Object obj) { 18 elementDate[size++] = obj; 19 } 20 21 public String toString() { 22 StringBuilder sb = new StringBuilder(); 23 24 sb.append("["); 25 for (int i = 0; i < size; i++) { 26 sb.append(elementDate[i]+","); 27 } 28 sb.setCharAt(sb.length()-1, \']\'); 29 return sb.toString(); 30 } 31 32 public static void main(String[] args) { 33 SxtArrayList s1 = new SxtArrayList(20); 34 s1.add("aa"); 35 s1.add("dd"); 36 37 System.out.println(s1); 38 } 39 }
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（2）数组的扩容操作
1 package cn.zjc.mycollection; 2 3 public class SxtArray01<E> { 4 private Object[] elementData; 5 private int size; 6 7 private static final int DEFALT_CAPACITY = 10; 8 9 public SxtArray01() { 10 elementData = new Object[DEFALT_CAPACITY]; 11 } 12 13 public SxtArray01(int capacity) { 14 elementData = new Object[capacity]; 15 } 16 17 public void add(E element) { 18 // 什么时候扩容 19 if (size == elementData.length) { 20 //怎么扩容(扩容操作） 21 Object[] newArray = new Object[elementData.length + (elementData.length >> 1)]; 22 System.arraycopy(elementData, 0, newArray, 0, elementData.length); 23 elementData = newArray; 24 } 25 elementData[size++] = element; 26 } 27 28 public String toString() { 29 StringBuilder sb = new StringBuilder(); 30 31 //[a,b,c] 32 sb.append("["); 33 for (int i = 0; i < size; i++) { 34 sb.append(elementData[i] + ","); 35 } 36 sb.setCharAt(sb.length() - 1, \']\'); 37 return sb.toString(); 38 } 39 40 public static void main(String[] args) { 41 SxtArray01 s1 = new SxtArray01(20); 42 43 for (int i = 0; i < 25; i++) { 44 s1.add("zh" + i); 45 } 46 System.out.println(s1); 47 } 48 }
运行结果图
（3）加get/set，索引不合法等
1 package cn.zjc.mycollection; 2 3 public class SxtArray01<E> { 4 private Object[] elementData; 5 private int size; 6 7 private static final int DEFALT_CAPACITY = 10; 8 9 public SxtArray01() { 10 elementData = new Object[DEFALT_CAPACITY]; 11 } 12 13 public SxtArray01(int capacity) { 14 elementData = new Object[capacity]; 15 } 16 17 public void add(E element) { 18 // 什么时候扩容 19 if (size == elementData.length) { 20 //怎么扩容(扩容操作） 21 Object[] newArray = new Object[elementData.length + (elementData.length >> 1)]; 22 System.arraycopy(elementData, 0, newArray, 0, elementData.length); 23 elementData = newArray; 24 } 25 elementData[size++] = element; 26 } 27 28 public E get(int index){ 29 checkRange(index); 30 return (E)elementData[index]; 31 } 32 33 public void set(E element,int index){ 34 checkRange(index); 35 elementData[index] = element; 36 } 37 public void checkRange(int index){ 38 //索引合法判断[0,size) 39 if (index<0||index>size-1){ 40 //不合法 41 throw new RuntimeException("索引不合法！"+index); 42 } 43 } 44 45 public String toString() { 46 StringBuilder sb = new StringBuilder(); 47 48 //[a,b,c] 49 sb.append("["); 50 for (int i = 0; i < size; i++) { 51 sb.append(elementData[i] + ","); 52 } 53 sb.setCharAt(sb.length() - 1, \']\'); 54 return sb.toString(); 55 } 56 57 public static void main(String[] args) { 58 SxtArray01 s1 = new SxtArray01(20); 59 60 for (int i = 0; i < 25; i++) { 61 s1.add("zh" + i); 62 } 63 s1.set("AAAAA",10); 64 System.out.println(s1); 65 System.out.println(s1.get(26)); 66 } 67 }
运行结果图
（4）链表的用法
1 package cn.zjc.mycollection; 2 3 public class Node { 4 Node previous; //上一个节点 5 Node next; //下一个节点 6 Object element; //元素数据 7 8 public Node(Node previous, Node next, Object element) { 9 this.previous = previous; 10 this.next = next; 11 this.element = element; 12 } 13 14 public Node(Object element) { 15 this.element = element; 16 } 17 }
1 package cn.zjc.mycollection; 2 3 /* 4 * 自定义一个链表 5 */ 6 public class SxtLinkedList01 { 7 8 private Node first; 9 private Node last; 10 11 private int size; 12 13 //插入节点操作 14 public void add(int index, Object obj) { 15 Node newNode = new Node(obj); 16 Node temp = getNode(index); 17 18 if (temp != null) { 19 Node up = temp.previous; 20 up.next = newNode; 21 newNode.previous = up; 22 23 newNode.next = temp; 24 temp.previous = newNode; 25 } 26 27 } 28 29 //remove方法 30 public void remove(int index) { 31 Node temp = getNode(index); 32 33 if (temp != null) { 34 Node up = temp.previous; 35 Node down = temp.next; 36 if (up != null) { 37 up.next = down; 38 } 39 if (down != null) { 40 down.previous = up; 41 } 42 //被删除的元素是第一个元素时 43 if (index == 0) { 44 first = down; 45 } 46 //被删除的元素是最后一个时 47 if (index == size - 1) { 48 last = up; 49 } 50 size--; 51 } 52 } 53 54 //get方法，传递索引，返回对应的内容 55 public Object get(int index) { 56 if (index < 0 || index > size - 1) { 57 throw new RuntimeException("索引数字不合法：" + index); 58 } 59 60 Node temp = getNode(index); 61 return temp != null ? temp.element : null; 62 } 63 64 public Node getNode(int index) { 65 Node temp = null; 66 67 if (index <= (size >> 1)) { 68 temp = first; 69 for (int i = 0; i < index; i++) { 70 temp = temp.next; 71 } 72 } else { 73 temp = last; 74 for (int i = size - 1; i > index; i--) { 75 temp = temp.previous; 76 } 77 } 78 return temp; 79 } 80 81 public void add(Object obj) { 82 Node node = new Node(obj); 83 84 if (first == null) { 85 86 first = node; 87 last = node; 88 } else { 89 node.previous = last; 90 node.next = null; 91 92 last.next = node; 93 last = node; 94 } 95 size++; 96 } 97 98 public String toString() { 99 Node temp以上是关于JAVA进阶20的主要内容，如果未能解决你的问题，请参考以下文章