Java8函数式接口的基础学习教程

public class RunnableDemo {

     public static void main(String[] args) {

         //在主方法中凋用startThread方法

         //匿名内部类

         startThread( new Runnable() {

             @Override

             public void run() {

                 System.out.println(Thread.currentThread().getName() + " 线程启动" );

             }

         });

         //Lambda

         startThread(() -> System.out.println(Thread.currentThread().getName() + " 线程启动" ));

     }

     private static void startThread(Runnable r) { //方法参数Runnable是一个凾数式接口

//      Thread t = new Thread(r);

//      t.start();

         new Thread(r).start();

     }

}

public class ComparatorDemo {

     public static void main(String[] args) {

         //构造使用场景 根据字符串长度

         //定义集合，存储字符串元素

         ArrayList<String> array = new ArrayList<String>();

         array.add( "Collin" );

         array.add( "Leon" );

         array.add( "Pi" );

         array.add( "123" );

         array.add( "878" );

         System.out.println( "排序前: " + array);

         Collections.sort(array);

         System.out.println( "排序后: " + array);

         Collections.sort(array, getComparator());

         System.out.println( "排序后: " + array);

     }

         private static Comparator<String> getComparator(){

                 //匿名内部类的方式实现

                 //根据长度去排序

//      Comparator<String > comp = new Comparator<String>() {

//             

//          @Override

//          public int compare(String o1, String o2) {

//              return o1.length() - o2.length();

//          }

//      };

//      return comp;

                 //改进

//      return new Comparator<String>() {

//             

//      @Override

//      public int compare(String o1, String o2) {

//          return o1.length() - o2.length();

//          }

//      };

                 //改进为Lambda表达式

//      return ((String s1, String s2) -> {

//          return s1.length()-s2.length();

//      });

                 //优化

                 return (s1,s2) -> s1.length()-s2.length();

         }

}

public class SupplierDemo {

     public static void main(String[] args) {

//      String s = getstring(() -> {

//          return "你好Java";

//      });

         //优化

         String s = getstring(() -> "略略略" );

         System.out.println(s);

         Integer i = getInteger(() -> 9920 );

         System.out.println(i);

     }

     //定义一个方法，返回一个int数据

     private static Integer getInteger(Supplier<Integer> sup) {

         return sup.get();

     }

     //定义一个方法，返回一个String数据

     private static String getstring(Supplier<String> sup) {

         return sup.get();

     }

}

     public static void main(String[] args) {

         operatorString( "Leo1" , (String s) ->{

             System.out.println(s);

         });

         //优化

         operatorString( "Leo2" , s -> System.out.println(s));

         //方法引用

         operatorString( "Leo3" , System.out::println);

         operatorString( "Leo4" , s -> System.out.println( new StringBuilder(s).reverse()));

         System.out.println( "--------------" );

         operatorString( "Leon5" , s -> System.out.println(s),s -> System.out.println( new StringBuilder(s).reverse()));

     }

     //定一个方法，用不同的方式消费同一个一个字符串数据俩次

     private static void operatorString(String name, Consumer<String> con1,Consumer<String> con2) {

//      con1.accept(name);

//      con2.accept(name);

         con1.andThen(con2).accept(name);

         //先消费name，再con2

     }

     //定一个方法，消费一个字符串数据

     private static void operatorString(String name, Consumer<String> con) {

         con.accept(name);

     }

}

public class ConsumerTest {

     public static void main(String[] args) {

         String[] strArray= { "林青霞,30" , "张曼玉,35" , "王祖贤,33" };

         printInfo(strArray, (String str) ->{

             String name = str.split( "," )[ 0 ];

             System.out.print( "Name: " + name);

         },(String str) -> {

             int age =Integer.parseInt(str.split( "," )[ 1 ]);

             System.out.println( " ,Age: " + age);

         });

         System.out.println( "-------------------" );

         //改进

         printInfo(strArray,

                 str -> System.out.print( "Name: " + str.split( "," )[ 0 ]),

                 str -> System.out.println( " ,Age: " + Integer.parseInt(str.split( "," )[ 1 ]))

                 );

     }

     private static void printInfo(String[] strArray, Consumer<String> con1, Consumer<String> con2) {

         for (String str : strArray) {

             con1.andThen(con2).accept(str);

         }

     }

}

public class PredicateTest {

     public static void main(String[] args) {

         String[] strArray= { "林青霞,30" , "柳岩,34" , "张曼玉,35" , "貂蝉,31" , "王祖贤,33" };

         ArrayList<String> array = myFilter(strArray,

                 s -> s.split( "," )[ 0 ].length() > 2 ,

                 s -> Integer.parseInt(s.split( "," )[ 1 ]) > 33 );

         for (String str : array) {

             System.out.println(str);

         }

     }

     //通过Predicate接口的拼装将符合要求的字符串筛选到集合ArrayList中

     private static ArrayList<String> myFilter(String[] strArray, Predicate<String> pre1, Predicate<String> pre2){

         //定义一个集合

         ArrayList<String> array = new ArrayList<String>();

         //遍历数组

         for (String str : strArray) {

             if (pre1.and(pre2).test(str)) {

                 array.add(str);

             }

         }

         return array;

     }

}

public class FunctionTest {

     public static void main(String[] args) {

         String s = "林青霞,30" ;

         convert(s, ss -> s.split( "," )[ 1 ], ss -> Integer.parseInt(ss), i -> i + 70 );

     }

     private static void convert(String s, Function<String, String> fun1, Function<String, Integer> fun2, Function<Integer, Integer> fun3) {

         int i = fun1.andThen(fun2).andThen(fun3).apply(s);

         System.out.println(i);

     }

}