Lambda表达式(一)

忘是亡心i 2023-06-08 05:59 65阅读 0赞

### 环境 gradle+idea ###

#### 1.创建项目： ####

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#### 2.1 lambda表达式初步介绍 匿名内部类 ####

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##### 2.1.1 如果是多行怎么写? #####

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package com.mff;
    
    import javax.swing.*;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    
    /** * @description: * @author: maofangfang * @time: 2019/10/16 17:28 */
    public class DemoTest { 
    
        public static void main(String[] args) { 
            JFrame jFrame = new JFrame("my JFeame");
            JButton jButton = new JButton("my Button");
            jButton.addActionListener(new ActionListener() { 
                @Override
                public void actionPerformed(ActionEvent e) { 
                    System.out.println("button ");
                }
            });
            jFrame.add(jButton);
            jFrame.pack();
            jFrame.setVisible(true);
            jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }
    }

##### 2.1.2 lambda表达式基本表达形式 #####

*  （param1，param2，param3）->\{ \}

#### 2.2 ####

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package com.mff;
    
    import javax.swing.*;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import java.util.Arrays;
    import java.util.List;
    import java.util.function.Consumer;
    
    /** * @description: * @author: maofangfang * @time: 2019/10/16 17:28 */
    public class DemoTest { 
        public static void main(String[] args) { 
            List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
            for (Integer integer : integers) { 
                System.out.print(integer);
            }
            
    
            System.out.println();
            System.out.println("---------");
            for (int i = 0; i < integers.size(); i++) { 
                System.out.print(integers.get(i));
            }
            
            System.out.println();
            System.out.println("---------");
    
            integers.forEach(new Consumer<Integer>() { 
                @Override
                public void accept(Integer integer) { 
                    System.out.print(integer);
                }
            });
    
        }
    
    }

#### 2.2.1 函数式接口 ####

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#### 2.2.2 关于函数式接口 ####

1.  如果一个接口只有一个抽象方法，那么该接口就是函数式接口。
2.  如果我们在一个接口上声明了 FunctionalInterface 注解，那么编译器就会按照函数式接口得定义来要求接口。
3.  如果一个接口只有一个抽象方法，但是我们没有给接口声明FunctionInterface注解，那么编译器依旧会将该接口看作是函数式接口。

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