从Java编程语言到编程思想

忘是亡心i 2023-06-22 05:29 34阅读 0赞

1、Java语法变化

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70][]

1.1 java1.3-1.4

public class Java3Demo {
    
        public static void main(String[] args) {
            /**
             * Java 1.2
             *  Collection Framework 2000
             *  Java Beans
             * Java 1.3
             * Java 1.4
             *  断言 assert 依赖编译参数
             *      assert -ea = enable
             *      assert -da = disable
             *  编程模型: fast-fail
             *      org.springframework.util.Assert
             *  堆栈跟踪
             *      增加两个构造器，在构造时将一异常来源记录到堆栈中
             *      Exception(Throwable cause)
             *      Exception(String message, Throwable cause)
             */
        }
    }

1.2 java1.5

public class Java5Demo {
    
        public static void main(String[] args) {
    
            /**
             * 泛型
             *  有了新的语言之后就会产生变化，继而产生新的编程模型
             */
            String[] values = new String[] {"hello", "world"};
            String[] values2 = of("hello", "world");
            Integer[] data = of(1, 2, 3);
        }
    
        private static <T> T[] of(T... values) {
            return values;
        }
    }

1.3 Java1.6&1.7

public class Java6Demo {
    
        /**
         * Override 是一个强约束，如果有 @Override ，编译器会检测；如果不加，编译器不会检测
         *
         * @return
         */
        @Override
        public String toString() {
            return super.toString();
        }
    }
    
    /**
     * Indicates that a method declaration is intended to override a
     * method declaration in a supertype. If a method is annotated with
     * this annotation type compilers are required to generate an error
     * message unless at least one of the following conditions hold:
     *
     * <ul><li>
     * The method does override or implement a method declared in a
     * supertype.
     * </li><li>
     * The method has a signature that is override-equivalent to that of
     * any public method declared in {@linkplain Object}.
     * </li></ul>
     *
     * @author  Peter von der Ahé
     * @author  Joshua Bloch
     * @jls 8.4.8 Inheritance, Overriding, and Hiding
     * @jls 9.4.1 Inheritance and Overriding
     * @jls 9.6.4.4 @Override
     * @since 1.5
     */
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.SOURCE)
    public @interface Override {
    }

public class Java7Demo {
    
        public static void main(String[] args) {
    
                /**
                 * 文件操作之后，要进行关闭操作
                 *  inputStream.read();
                 *  inputStream.close();
                 *
                 * 在1.7之前，我们通过try{} finally{} 在finally中释放资源。
                 *  在finally中关闭资源存在以下问题：
                 *      1、自己要手动写代码做关闭的逻辑；
                 *      2、有时候还会忘记关闭一些资源；
                 *      3、关闭代码的逻辑比较冗长，不应该是正常的业务逻辑需要关注的；
                 *
                 * 在1.7之后，新增try-catch的特性，不需要我们在 finally 中关闭，可以通过 try-catch 语法来自动关闭
                 * 对于实现AutoCloseable接口的类的实例，将其放到try后面（我们称之为：带资源的try语句），在try结束的时候，会自动将这些资源关闭（调用close方法）。
                 *  AutoCloseable since 1.7
                 *      JDBC Connection
                 *      InputStream
                 *      ...
                 */
            try (FileInputStream inputStream = new FileInputStream("D:/test.txt")) {
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    }
    
    public class Java7Demo2 {
    
        public static void main(String[] args) {
    
            try(AutoCloseableObject object = new AutoCloseableObject()) {
                System.out.println("--执行中--");
            } catch (Exception e) {
                System.out.println("--exception--");
            } finally {
                System.out.println("--finally--");
            }
        }
    
        public static class AutoCloseableObject implements AutoCloseable {
    
            @Override
            public void close() throws Exception {
                System.out.println("--close--");
            }
        }
    }

1.4 Java1.9&1.10

/**
     * 模块化，国内不常用
     */
    module javase {
        requires java.sql;
        exports com.imooc.demo;
    }

public class Java10Demo {
    
        public static void main(String[] args) {
    
            /**
             * 兼容多语言（JS）
             * JDK 1.6 Rihno JS on JVM
             */
            var a = new ArrayList<>();
        }
    }

2.、Java 数据结构

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 1][]

3、Java 类库提升

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 2][]

4、Java 编程模型

面向对象编程(OOP)、面向切面编程(AOP)、面向元信息编程(MDOP)、面向函数编程(FOP)、面向模块编程(MOP)

4.1 面向对象编程(OOP)

封装性
        决定了数据访问的限制
    派生性
        决定上下游关系
    多态性
        一种接口多种实现

4.2 面向切面变成(AOP)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 4][]

4.3 面向元信息编程(MDOP)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 5][]

4.4 面向函数编程(FOP)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 6][]

5、Java编程思想

契约编程、设计模式、模式驱动

5.1 契约编程

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 7][]

5.2 设计模式

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 8][]

5.3 驱动模式

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L20wXzM3NzMyODI5_size_16_color_FFFFFF_t_70 9][]

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