JAVA进阶20

浅浅的花香味﹌ 2021-09-29 03:22 352阅读 0赞

1、可视化日历程序（简陋版）

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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

![1179853-20190411112405114-448082491.png][]

2、使用递归打印目录树结构

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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

![1179853-20190411121218704-972164523.png][]

3、枚举的用法

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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

![1179853-20190411141111271-180661812.png][]

4、异常处理

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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

![1179853-20190411151005924-1988688627.png][]

5、容器和数据结构

（1）简化版-手工实现ArrayList

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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 }

运行结果图

![1179853-20190412102454318-1920237608.png][]

（2）数组的扩容操作

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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

![1179853-20190412152524567-197129374.png][]

（3）加get/set，索引不合法等

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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

![1179853-20190412164458395-296961589.png][]

（4）链表的用法

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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 }

Node

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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 = first;
    100         while (temp != null) {
    101             System.out.println(temp.element);
    102             temp = temp.next;
    103         }
    104         return "";
    105     }
    106 
    107 
    108     public static void main(String[] args) {
    109         SxtLinkedList01 list = new SxtLinkedList01();
    110 
    111         list.add("a");
    112         list.add("d");
    113         list.add("c");
    114         list.add("1");
    115         list.add("3");
    116         list.add("A");
    117 
    118         System.out.println(list);
    119         System.out.println(list.get(2));
    120         System.out.println("==============");
    121         list.remove(1);
    122         System.out.println(list);
    123         System.out.println("==============");
    124         list.add(2,"黄飞鸿");
    125         System.out.println(list);
    126     }
    127 }

运行结果图

![1179853-20190415150215689-833283091.png][]

转载于:https://www.cnblogs.com/Anemia-BOY/p/10691520.html

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[1179853-20190415150215689-833283091.png]: https://img2018.cnblogs.com/blog/1179853/201904/1179853-20190415150215689-833283091.png