JAVA进阶20

1、可视化日历程序（简陋版）

package cn.zh.abstrac;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Scanner;

public class TestCalendar {
    public static void main(String[] args) throws ParseException {
        System.out.println("请输入一个日期：（格式：yyyy-MM-dd）");
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
        Date date = df.parse(str);
        Calendar c = new GregorianCalendar();
        c.setTime(date);

        int day = c.get(Calendar.DAY_OF_MONTH);
        int days = c.getActualMaximum(Calendar.DATE);
        System.out.println("日	一	二	三	四	五	六");

        c.set(Calendar.DAY_OF_MONTH, 1);

        for (int i = 0; i < c.get(Calendar.DAY_OF_WEEK) - 1; i++) {
            System.out.print  ("	");
        }

        for (int i = 1; i <= days; i++) {
            if (day == c.get(Calendar.DAY_OF_MONTH)){
                System.out.print(c.get(Calendar.DAY_OF_MONTH) + "*	");
            }else {
                System.out.print(c.get(Calendar.DAY_OF_MONTH) + "	");
            }


            if (c.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) {
                System.out.println();       //换行
            }
            c.add(Calendar.DAY_OF_MONTH, 1);
        }
    }
}

运行结果图

2、使用递归打印目录树结构

package cn.zh.abstrac;

import java.io.File;

public class TestFile {
    public static void main(String[] args) {
        File f = new File("E:\小程序");
        printFile(f,0 );
    }

    static void printFile(File file,int level) {
        //输出层次
        for (int i = 0; i < level; i++) {
            System.out.print("-");
        }
        System.out.println(file.getName());
        if (file.isDirectory()) {
            File[] files = file.listFiles();

            for (File temp : files) {
                printFile(temp,level+1);
            }
        }

    }
}

运行结果图

3、枚举的用法

package cn.zh.abstrac;

import java.util.Random;

public class TestEnum {
    public static void main(String[] args) {
        //枚举遍历
        for (week k : week.values()) {
            System.out.println(k);
        }
        //switch语句中使用枚举
        int a = new Random().nextInt(4);  //生成0,1,2,3的随机数
        switch (Season.values()[a]) {
            case SPRING:
                System.out.println("春天");
                break;
            case SUMMER:
                System.out.println("夏天");
                break;
            case AUTUMN:
                System.out.println("秋天");
                break;
            case WINTER:
                System.out.println("冬天");
                break;
        }
    }
}
enum Season{
    SPRING,SUMMER,AUTUMN,WINTER
}
enum week{
    星期一,星期二,星期三,星期四,星期五,星期六,星期日,
}

运行结果图

4、异常处理

package cn.zh.abstrac;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class TestA {
    public static void main(String[] args) {
        FileReader reader = null;
        try {
            reader = new FileReader("d:/a.txt");
            System.out.println("111111111");
            char c = (char)reader.read();
            char c1 =  (char)reader.read();
            System.out.println(""+c+c1);
        }catch (FileNotFoundException e){
            System.out.println("2222222222222222");
            e.printStackTrace();
        }catch (IOException e){
            e.printStackTrace();
        }finally {
            System.out.println("333333333333333333");
            try {
                if(reader !=null){
                    reader.close();
                }
            }
            catch (Exception e){
                e.printStackTrace();

            }
        }
    }
}

运行结果图

5、容器和数据结构

（1）简化版-手工实现ArrayList

package cn.zjc.mycollection;

public class SxtArrayList {
    private Object[] elementDate;
    private int size;

    private static final int DEFALT_CAPACITY = 10;

    public SxtArrayList() {
        elementDate = new Object[DEFALT_CAPACITY];
    }

    public SxtArrayList(int capacity) {
        elementDate = new Object[capacity];
    }

    public void add(Object obj) {
        elementDate[size++] = obj;
    }

    public String toString() {
        StringBuilder sb = new StringBuilder();

        sb.append("[");
        for (int i = 0; i < size; i++) {
            sb.append(elementDate[i]+",");
        }
        sb.setCharAt(sb.length()-1, ']');
        return sb.toString();
    }

    public static void main(String[] args) {
        SxtArrayList s1 = new SxtArrayList(20);
        s1.add("aa");
        s1.add("dd");

        System.out.println(s1);
    }
}

 运行结果图

（2）数组的扩容操作

package cn.zjc.mycollection;

public class SxtArray01<E> {
    private Object[] elementData;
    private int size;

    private static final int DEFALT_CAPACITY = 10;

    public SxtArray01() {
        elementData = new Object[DEFALT_CAPACITY];
    }

    public SxtArray01(int capacity) {
        elementData = new Object[capacity];
    }

    public void add(E element) {
        // 什么时候扩容
        if (size == elementData.length) {
            //怎么扩容(扩容操作）
            Object[] newArray = new Object[elementData.length + (elementData.length >> 1)];
            System.arraycopy(elementData, 0, newArray, 0, elementData.length);
            elementData = newArray;
        }
        elementData[size++] = element;
    }

    public String toString() {
        StringBuilder sb = new StringBuilder();

        //[a,b,c]
        sb.append("[");
        for (int i = 0; i < size; i++) {
            sb.append(elementData[i] + ",");
        }
        sb.setCharAt(sb.length() - 1, ']');
        return sb.toString();
    }

    public static void main(String[] args) {
        SxtArray01 s1 = new SxtArray01(20);

        for (int i = 0; i < 25; i++) {
            s1.add("zh" + i);
        }
        System.out.println(s1);
    }
}

 运行结果图

 

（3）加get/set，索引不合法等

package cn.zjc.mycollection;

public class SxtArray01<E> {
    private Object[] elementData;
    private int size;

    private static final int DEFALT_CAPACITY = 10;

    public SxtArray01() {
        elementData = new Object[DEFALT_CAPACITY];
    }

    public SxtArray01(int capacity) {
        elementData = new Object[capacity];
    }

    public void add(E element) {
        // 什么时候扩容
        if (size == elementData.length) {
            //怎么扩容(扩容操作）
            Object[] newArray = new Object[elementData.length + (elementData.length >> 1)];
            System.arraycopy(elementData, 0, newArray, 0, elementData.length);
            elementData = newArray;
        }
        elementData[size++] = element;
    }

    public E get(int index){
        checkRange(index);
        return (E)elementData[index];
    }

    public void set(E element,int index){
        checkRange(index);
        elementData[index] = element;
    }
    public void checkRange(int index){
        //索引合法判断[0,size)
        if (index<0||index>size-1){
            //不合法
            throw new RuntimeException("索引不合法！"+index);
        }
    }

    public String toString() {
        StringBuilder sb = new StringBuilder();

        //[a,b,c]
        sb.append("[");
        for (int i = 0; i < size; i++) {
            sb.append(elementData[i] + ",");
        }
        sb.setCharAt(sb.length() - 1, ']');
        return sb.toString();
    }

    public static void main(String[] args) {
        SxtArray01 s1 = new SxtArray01(20);

        for (int i = 0; i < 25; i++) {
            s1.add("zh" + i);
        }
        s1.set("AAAAA",10);
        System.out.println(s1);
        System.out.println(s1.get(26));
    }
}

 运行结果图

（4）链表的用法

package cn.zjc.mycollection;

public class Node {
    Node previous;      //上一个节点
    Node next;           //下一个节点
    Object element;     //元素数据

    public Node(Node previous, Node next, Object element) {
        this.previous = previous;
        this.next = next;
        this.element = element;
    }

    public Node(Object element) {
        this.element = element;
    }
}

package cn.zjc.mycollection;

/*
 * 自定义一个链表
 */
public class SxtLinkedList01 {

    private Node first;
    private Node last;

    private int size;

    //插入节点操作
    public void add(int index, Object obj) {
        Node newNode = new Node(obj);
        Node temp = getNode(index);

        if (temp != null) {
            Node up = temp.previous;
            up.next = newNode;
            newNode.previous = up;

            newNode.next = temp;
            temp.previous = newNode;
        }

    }

    //remove方法
    public void remove(int index) {
        Node temp = getNode(index);

        if (temp != null) {
            Node up = temp.previous;
            Node down = temp.next;
            if (up != null) {
                up.next = down;
            }
            if (down != null) {
                down.previous = up;
            }
            //被删除的元素是第一个元素时
            if (index == 0) {
                first = down;
            }
            //被删除的元素是最后一个时
            if (index == size - 1) {
                last = up;
            }
            size--;
        }
    }

    //get方法，传递索引，返回对应的内容
    public Object get(int index) {
        if (index < 0 || index > size - 1) {
            throw new RuntimeException("索引数字不合法：" + index);
        }

        Node temp = getNode(index);
        return temp != null ? temp.element : null;
    }

    public Node getNode(int index) {
        Node temp = null;

        if (index <= (size >> 1)) {
            temp = first;
            for (int i = 0; i < index; i++) {
                temp = temp.next;
            }
        } else {
            temp = last;
            for (int i = size - 1; i > index; i--) {
                temp = temp.previous;
            }
        }
        return temp;
    }

    public void add(Object obj) {
        Node node = new Node(obj);

        if (first == null) {

            first = node;
            last = node;
        } else {
            node.previous = last;
            node.next = null;

            last.next = node;
            last = node;
        }
        size++;
    }

    public String toString() {
        Node temp = first;
        while (temp != null) {
            System.out.println(temp.element);
            temp = temp.next;
        }
        return "";
    }


    public static void main(String[] args) {
        SxtLinkedList01 list = new SxtLinkedList01();

        list.add("a");
        list.add("d");
        list.add("c");
        list.add("1");
        list.add("3");
        list.add("A");

        System.out.println(list);
        System.out.println(list.get(2));
        System.out.println("==============");
        list.remove(1);
        System.out.println(list);
        System.out.println("==============");
        list.add(2,"黄飞鸿");
        System.out.println(list);
    }
}

 运行结果图