一、多线程
1、线程的创建、启动、停止、休眠、等待
public class ThreadDemo extends Thread {
public void run(){
System.out.println("线程的执行");
}
public static void main(String[] args){
ThreadDemo thread = new ThreadDemo();
thread.start(); // 启动线程
}
}
2、线程池的使用
public class ThreadPoolDemo {
public static void main(String[] args){
ExecutorService executorService = Executors.newFixedThreadPool(5); // 创建固定大小的线程池
for(int i=0; i<10; i++){
executorService.execute(new Runnable() {
public void run() {
System.out.println(Thread.currentThread().getName() + "正在执行任务");
}
});
}
executorService.shutdown(); // 关闭线程池
}
}
3、线程间的通信
public class ThreadCommunicationDemo {
public static void main(String[] args) {
final Business business = new Business();
new Thread(new Runnable() {
public void run() {
for(int i=0; i<50; i++){
business.sub();
}
}
}).start();
for(int i=0; i<50; i++){
business.main();
}
}
static class Business{
private boolean flag = true;
public synchronized void main(){
if(flag){
try {
this.wait(); // 如果flag为true，则等待
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for(int i=0; i<5; i++){
System.out.println(Thread.currentThread().getName() + "运行第" + i + "次");
}
flag = true; // 设置flag为true
this.notify(); // 通知
}
public synchronized void sub(){
if(!flag){
try {
this.wait(); // 如果flag为false，则等待
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for(int i=0; i<10; i++){
System.out.println(Thread.currentThread().getName() + "运行第" + i + "次");
}
flag = false; // 设置flag为false
this.notify(); // 通知
}
}
}
二、异常处理
1、try-catch-finally语句块
public class TryCatchFinallyDemo {
public static void main(String[] args){
try {
int i = 1 / 0;
} catch (Exception e) {
e.printStackTrace();
} finally{
System.out.println("finally语句块");
}
}
}
2、自定义异常类
public class CustomExceptionDemo {
public static void main(String[] args) throws CustomException{
int age = 10;
if(age < 18){
throw new CustomException("未满18周岁，无法注册");
} else {
System.out.println("注册成功");
}
}
}
class CustomException extends Exception{
public CustomException(String message){
super(message);
}
}
3、finally语句块中的return语句
public class FinallyReturnDemo {
public static void main(String[] args) {
System.out.println(getNum());
}
public static int getNum(){
try {
return 1;
} finally{
return 2;
}
}
}
三、泛型
1、泛型类、泛型方法
public class GenericDemo{ private T t; public void setT(T t) { this.t = t; } public T getT() { return t; } public void printMsg(E e){ System.out.println(e.getClass()); } public static void main(String[] args){ GenericDemo genericDemo = new GenericDemo (); genericDemo.setT("JAVA高级编程开发技巧"); System.out.println(genericDemo.getT()); genericDemo.printMsg("泛型方法"); // 输出java.lang.String GenericDemo genericDemo1 = new GenericDemo (); genericDemo1.setT(2019); System.out.println(genericDemo1.getT()); genericDemo1.printMsg(123); // 输出java.lang.Integer } }
2、泛型接口
public interface GenericInterface{ public void setT(T t); public T getT(); public void printMsg(String msg); } class GenericImpl implements GenericInterface { private T t; public void setT(T t) { this.t = t; } public T getT() { return t; } public void printMsg(String msg) { System.out.println(msg + "：" + t); } public static void main(String[] args){ GenericInterface genericInterface = new GenericImpl (); genericInterface.setT("泛型接口"); System.out.println(genericInterface.getT()); genericInterface.printMsg("JAVA高级编程开发技巧"); } }
四、注解
1、自定义注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
public String value() default "自定义注解";
}
@MyAnnotation
public class AnnotationDemo {
public static void main(String[] args){
Annotation[] annotations = AnnotationDemo.class.getAnnotations();
for(Annotation annotation : annotations){
if(annotation instanceof MyAnnotation){
MyAnnotation myAnnotation = (MyAnnotation) annotation;
System.out.println(myAnnotation.value()); // 输出自定义注解
}
}
}
}
2、元注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface MyAnnotation {
public String value() default "元注解";
}
@MyAnnotation
public class AnnotationDemo {
public static void main(String[] args){
Annotation[] annotations = AnnotationDemo.class.getAnnotations();
for(Annotation annotation : annotations){
if(annotation instanceof MyAnnotation){
MyAnnotation myAnnotation = (MyAnnotation) annotation;
System.out.println(myAnnotation.value()); // 输出元注解
}
}
}
}
五、高级特性
1、反射机制
public class ReflectionDemo {
public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
// 获取类的Class对象
Class clazz = Class.forName("com.reflection.Test");
Object object = clazz.newInstance();
// 获取类的构造方法
Constructor constructor = clazz.getDeclaredConstructor();
constructor.setAccessible(true);
Object object1 = constructor.newInstance();
// 获取类的私有方法
Method method = clazz.getDeclaredMethod("privateMethod", String.class);
method.setAccessible(true);
method.invoke(object, "JAVA高级编程开发技巧");
// 获取类的字段
Field field = clazz.getDeclaredField("name");
field.setAccessible(true);
field.set(object1, "reflnation");
System.out.println(field.get(object1));
}
}
class Test {
private String name;
public Test(){
this.name = "Java";
}
private void privateMethod(String msg){
System.out.println("私有方法：" + msg);
}
}
2、动态代理
public interface Service {
public void add();
public void update();
}
public class ServiceImpl implements Service{
public void add() {
System.out.println("添加用户");
}
public void update() {
System.out.println("修改用户");
}
}
public class ProxyDemo {
public static void main(String[] args) {
Service service = new ServiceImpl();
Service proxy = (Service) Proxy.newProxyInstance(service.getClass().getClassLoader(), service.getClass().getInterfaces(), new InvocationHandler() {
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println(method.getName() + "开始执行");
Object result = method.invoke(service, args);
System.out.println(method.getName() + "执行完成");
return result;
}
});
proxy.add();
proxy.update();
}
}
