这一个星期学到的有：异常，集合，IO流，多线程。
异常
1.我个人理解异常就是在程序运行的过程中发生一些不正常的事件，它会结束正在运行的程序。
2.Java异常处理：Java它有对异常处理的能力，Java有5个关键字来处理异常：try、catch、finally、throw、throwstry：它执行可能产生异常的代码catch：它是用来捕获异常的finally：它是无论程序出不出现异常，它都会执行的代码throw：自动抛出异常和手动抛出异常throws：声明方法可能要抛出的各种异常public static void main(String[] args) { // TODO Auto-generated method stub // 异常 try { System.out.print("请输入第一个数:"); Scanner scanner = new Scanner(System.in); int a = scanner.nextInt(); System.out.print("请输入第一个数:"); int b = scanner.nextInt(); System.out.println(a / b); } catch (InputMismatchException exception) { System.out.println("除数和被除数必须为正数"); } catch (ArithmeticException exception) { System.out.println("除数不能为0"); } catch (Exception e) { System.out.println("其它异常"); } finally { System.out.println("谢谢使用"); } } public static void main(String[] args) { // TODO Auto-generated method stub try { Scanner scanner = new Scanner(System.in); System.out.print("请输入课程代号(1~3之间的数字):"); int a = scanner.nextInt(); switch (a) { case 1: System.out.println("C#编程"); break; case 2: System.out.println("C语言"); break; case 3: System.out.println("JAVA"); break; default: System.out.println("只能输入1~3之间的数字"); break; } } catch (InputMismatchException exception) { System.out.println("输入的数字必须为数字"); } finally { System.out.println("欢迎提出建议"); } } public static void main(String[] args) { // TODO Auto-generated method stub try { Person person = new Person(); person.setAge(10); person.setSex("无"); System.out.println("创建成功"); } catch (Exception e) { System.err.println(e.getMessage()); } finally { System.out.println("人是一个高等级动物"); } }}class Person { private int age; private String sex; // public int getAge() { return age; } //throws Exception是一个异常抛出的管道 public void setAge(int age) throws Exception { if (age > 0) { this.age = age; } else { throw new Exception("年龄必须大于0"); //创建的异常对象 } } public String getSex() { return sex; } public void setSex(String sex) throws Exception { if ("男".equals(sex) || "女".equals(sex)) { this.sex = sex; } else { throw new Exception("必须是男或女"); } } 这些是我做的练习
集合
1.collection集合：list 、set
2.list: arrayList 、LinkedList3.arrayListarrayList
public class Demo01 { public static void main(String[] args) { // TODO Auto-generated method stub List list = new ArrayList(); list.add(new Dog("强强", 12)); list.add(new Dog("球球", 12)); list.add(new Dog("希希", 12)); list.add(1, new Dog("安安", 11)); Dog dog2 = new Dog("大大", 13); list.add(dog2); // 删除 // E remove(int index) // 移除此列表中指定位置上的元素。 // boolean remove(Object o) // 移除此列表中首次出现的指定元素。 list.remove(0); list.remove(dog2); // list.clear();// 移除全部 // 查询 list.set(1, new Dog("丽丽", 12)); for (int i = 0; i < list.size(); i++) { // get是索取某个索引位置上的内容 Dog dog = (Dog) list.get(i); System.out.println(dog.toString()); } }} LinkedList
public class Demo01 { public static void main(String[] args) { // TODO Auto-generated method stub LinkedList list = new LinkedList();// 父类引用指向子类对象 // 创建对象 Dog pingping = new Dog("平平", 2); Dog tutu = new Dog("兔兔", 2); Dog tu2 = new Dog("图图", 2); // 添加到集合中 list.add(pingping); list.addFirst(tutu); list.addLast(tu2); // 获得第一个元素 System.out.println(list.getFirst().toString()); System.out.println(list.getLast().toString()); // 删除第一个 list.removeFirst(); list.removeLast(); System.out.println("~~~~~~~~~~~~"); for (int i = 0; i < list.size(); i++) { Dog dog = (Dog) list.get(i); System.out.println(dog.toString()); } }} 4.set:hashset
hashset
public class Demo04 { public static void main(String[] args) { // TODO Auto-generated method stub Set set = new HashSet (); Random random = new Random(); while (set.size() <= 10) { set.add(random.nextInt(20) + 1); } for (Integer integer : set) { System.out.println(integer); } }} public class Demo05 { public static void main(String[] args) { // TODO Auto-generated method stub //去除重复的字符 Scanner scanner = new Scanner(System.in); System.out.print("请输入一段字符:"); String aString = scanner.nextLine(); System.out.println(aString); HashSet hs = new HashSet (); char[] arr = aString.toCharArray(); for (char c : arr) { hs.add(c); } for (Character ch : hs) { System.out.print(ch); } }} 5.泛型
泛型就是允许在编写集合的时候，先限制集合的数据处理类型
6.Map
map：将键映射到值的对象，一个映射不能包含重复的键；每个键最多只能映射到一个值
HashMap
public static void main(String[] args) { // TODO Auto-generated method stub Map map = new HashMap(); Scanner scanner = new Scanner(System.in); System.out.print("请输入一段字符串:"); String a = scanner.next(); char[] chars = a.toCharArray(); for (char c : chars) { if (map.containsKey(c)) { map.put(c, map.get(c) + 1); } else { map.put(c, 1); } } for (Character character : map.keySet()) { System.out.println(character + ":" + map.get(character)); } } 7.遍历
list遍历可以用for循环也可以用foreach
set只能用foreach8.迭代器
public static void main(String[] args) { // TODO Auto-generated method stub Map map = new HashMap (); // put方法如果集合当中没有对应键值则新增，如果有则修改; map.put("YL", "yl"); map.put("LY", "ly"); map.put("XY", "xy"); /* * //第一种迭代器 //获取所有的键 并且存放到set集合中; Set set = map.keySet(); * //set集合的迭代器; Iterator iterator = set.iterator(); * //首先判断set集合中是否有下一个元素; //如果有则获取下一个元素; while (iterator.hasNext()) { * //next:获取当前指针指向的对象的引用,获得之后,自己把指针向后移一位; String iString = * iterator.next(); System.out.println(iString + "\t" + * map.get(iString)); } */ // 第二种迭代器 Set > set2 = map.entrySet(); for (Map.Entry entry : set2) { System.out.println(entry); } } IO流
1.file类：就是文件在系统当中具体的位置
2.创建文件和文件夹public static void main(String[] args) { // TODO Auto-generated method stub // Demo01(); // Demo02(); File file = new File("E:\\JAVA\\新建文件夹"); if (file.mkdirs()) { System.out.println("创建成功"); } else { System.out.println("创建失败"); } } private static void Demo02() { File file = new File("E:\\JAVA\\新建文件夹\\abd"); if (file.mkdir()) { System.out.println("创建成功"); } else { System.out.println("创建失败"); } } // 创建空的文件 private static void Demo01() { File file = new File("E:\\JAVA\\新建文件夹\\abd.txt"); try { // file.createNewFile(); if (file.createNewFile()) { System.out.println("创建成功"); } else { System.out.println("创建失败"); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } 3.重命名和删除
public static void main(String[] args) { // Demo01(); File newfile = new File("E:\\JAVA\\新建文件夹\\abd2"); if (newfile.delete()) { System.out.println("删除成功"); } } // 修改 private static void Demo01() { File file = new File("E:\\JAVA\\新建文件夹\\abd"); // 新的路径 File newfile = new File("E:\\JAVA\\新建文件夹\\abd2"); if (file.renameTo(newfile)) { System.out.println("修改成功"); } else { System.out.println("修改失败"); } } io流
1.io流：Java对数据的读写（传输）操作通过流的方式
2.字节流：可以操作任何数据3.字符流：用于操作纯字符文件字节流
public static void main(String[] args) throws IOException { // TODO Auto-generated method stub // 创建输入流 FileInputStream fileInputStream = new FileInputStream( "E:\\JAVA\\新建文件夹\\一生所爱.flac"); // 2、创建输出流 FileOutputStream fStream = new FileOutputStream("E:\\JAVA\\新建文件夹\\一生所爱2.flac"); // 3、读写 int b; while ((b = fileInputStream.read()) != -1) { fStream.write(b); } fileInputStream.close(); fStream.close(); } 字符流
public static void main(String[] args) { // TODO Auto-generated method stub FileReader fileReader = null; FileWriter fileWriter = null; try { fileReader = new FileReader("E:\\JAVA\\IO流\\爱你.txt"); fileWriter = new FileWriter("E:\\JAVA\\IO流\\爱你爱你.txt"); int c; while ((c = fileReader.read()) != -1) { fileWriter.write(c); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { try { fileReader.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { fileWriter.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } public static void main(String[] args) { // TODO Auto-generated method stub BufferedReader bf = null; BufferedWriter bw = null; try { bf = new BufferedReader(new FileReader("E:\\JAVA\\IO流\\abc.txt")); String line = null; StringBuffer stringBuffer = new StringBuffer(); while ((line = bf.readLine()) != null) { stringBuffer.append(line); } System.out.println("替换前:" + stringBuffer); bw = new BufferedWriter(new FileWriter("E:\\JAVA\\IO流\\abc.txt")); // 替换字符 String string = stringBuffer.toString().replace("name", "XL").replace("type", "哈士奇").replace("master", "AL"); bw.write(string); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } finally { try { bf.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { bw.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } 多线程
1.多线程：程序执行的多个路径
2.多线程并发：可以提高程序的执行效率，可以同时完成多个任务3.多线程的运行：多个程序同时在运行4.实现多线程运行的方式：1.子类继承thread类，重写run方法。当执行start方法时，直接执行子类的run方法 2.实现runnable接口public static void main(String[] args) { // TODO Auto-generated method stub Mythread mythread = new Mythread(); Mythread mythread2 = new Mythread(); mythread.setName("你好,来自线程" + mythread); mythread.start(); mythread2.setName("你好,来自线程" + mythread2); mythread2.start(); }}class Mythread extends Thread { public void run() { for (int i = 0; i < 20; i++) { System.out.println(Thread.currentThread().getName() + ":" + i); } }} 休眠线程
public static void main(String[] args) { // TODO Auto-generated method stub // DemoA(); for (int i = 10; i > 0; i--) { try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("敌军还有:" + i + "S到达战场"); } System.out.println("全军出击"); } // ******************************************************************** private static void DemoA() { new Thread() { public void run() { for (int i = 0; i < 10; i++) { System.out.println(Thread.currentThread().getName() + "：" + i); try { Thread.sleep(1500); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }.start(); new Thread() { public void run() { for (int i = 0; i < 10; i++) { System.out.println(Thread.currentThread().getName() + "：" + i); try { Thread.sleep(1500); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }.start(); }} 线程的优先级
public static void main(String[] args) { // TODO Auto-generated method stub Thread thread = new Thread(new MyThread2(), "线程A"); Thread thread2 = new Thread(new MyThread2(), "线程B"); // 设置线程的优先级 thread.setPriority(thread.MAX_PRIORITY); thread2.setPriority(thread.MIN_PRIORITY); thread.start(); thread2.start(); System.out.println(thread.getPriority()); System.out.println(thread2.getPriority()); }}class MyThread2 implements Runnable { @Override public void run() { // TODO Auto-generated method stub for (int i = 0; i < 100; i++) { System.out.println(Thread.currentThread().getName() + "~~~~~~" + i); } }} 接口实现线程
public static void main(String[] args) { // TODO Auto-generated method stub // 创建线程对象 MyRunnable myRunnable = new MyRunnable(); // 开启线程 Thread thread = new Thread(myRunnable); Thread thread2 = new Thread(myRunnable); thread.start(); thread2.start(); }}class MyRunnable implements Runnable { @Override public void run() { // TODO Auto-generated method stub for (int i = 0; i < 10; i++) { System.out.println(Thread.currentThread().getName() + ":" + i); } }} 多线程执行状态
public static void main(String[] args) { // TODO Auto-generated method stub Thread thread = new Thread(new MyThread3()); System.out.println("线程已创建"); thread.start(); System.out.println("线程就绪"); }}class MyThread3 implements Runnable { @Override public void run() { // TODO Auto-generated method stub System.out.println("程序在运行"); try { System.out.println("马上进入休眠期"); Thread.sleep(1000); System.out.println("经过短暂的休眠之后"); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } }} 线程的礼让
public static void main(String[] args) { // TODO Auto-generated method stub Thread thread = new Thread(new Mythread5(), "线程A"); Thread thread2 = new Thread(new Mythread5(), "线程B"); thread.start(); thread2.start(); }}class MyThread5 implements Runnable { @Override public void run() { // TODO Auto-generated method stub for (int i = 0; i < 5; i++) { System.out.println(Thread.currentThread().getName() + "正在运行"); if (i == 3) { System.out.println("线程的礼让"); Thread.yield(); } } } 多线程练习题
public static void main(String[] args) { // TODO Auto-generated method stub Thread thread = new Thread(new MyThread4()); thread.setPriority(10); thread.start(); for (int i = 1; i < 50; i++) { System.out.println("普通号:" + i + "号病人在看病"); try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } if (i == 10) { try { thread.join(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }}class MyThread4 implements Runnable { // 特需号 @Override public void run() { // TODO Auto-generated method stub for (int i = 1; i < 11; i++) { try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("特需号:" + i + "号病人在看病!"); } }}这些就是一星期的总结