Lambda作用域

Author: MyHerux

src/main/java/com/xu/java8/lambda/InterfaceT.java

@@ -35,6 +35,8 @@ public double calculate(int a) {
         System.out.println(formula1.sqrt(-23));
         System.out.println(Formula.positive(-4));
 
+        /**Lambda表达式不能使用默认方法，无法编译*/
+        //Formula formula = (a) -> sqrt( a * 100);
     }
 }
 

src/main/java/com/xu/java8/lambda/Lambda4.java

@@ -1,7 +1,7 @@
 package com.xu.java8.lambda;
 
 /**
- * Class Lambda作用域。
+ * Class Lambda作用域。访问局部变量,对象字段与静态变量
  *
  * @author hua xu
  * @version 1.0.0
@@ -17,29 +17,39 @@ public class Lambda4 {
     int outerNum;
 
     void testScopes() {
+
+        /**变量num可以不用声明为final*/
         int num = 1;
 
+        /**可以直接在lambda表达式中访问外层的局部变量*/
         Lambda2.Converter<Integer, String> stringConverter =
                 (from) -> String.valueOf(from + num);
-
         String convert = stringConverter.convert(2);
         System.out.println(convert);    // 3
+        /**但是num必须不可被后面的代码修改（即隐性的具有final的语义），否则编译出错*/
+        //num=3;
 
+        /**lambda内部对于实例的字段以及静态变量是即可读又可写*/
         Lambda2.Converter<Integer, String> stringConverter2 = (from) -> {
             outerNum = 13;
-            return String.valueOf(from);
+            return String.valueOf(from + outerNum);
         };
+        System.out.println(stringConverter2.convert(2));
+        System.out.println("\nBefore:outerNum-->"+outerNum);
+        outerNum=15;
+        System.out.println("After:outerNum-->"+outerNum);
 
         String[] array = new String[1];
         Lambda2.Converter<Integer, String> stringConverter3 = (from) -> {
-            array[0] = "Hi there";
+            array[0] = "Hi here";
             return String.valueOf(from);
         };
-
         stringConverter3.convert(23);
-
-        System.out.println(array[0]);
+        System.out.println("\nBefore:array[0]-->"+array[0]);
+        array[0] = "Hi there";
+        System.out.println("After:array[0]-->"+array[0]);
     }
+
     public static void main(String[] args) {
         new Lambda4().testScopes();
     }

src/main/java/com/xu/java8/lambda/Lambda5.java

@@ -0,0 +1,36 @@
+package com.xu.java8.lambda;
+
+import java.util.HashMap;
+import java.util.function.BiConsumer;
+
+/**
+ * Class description
+ *
+ * @author hua xu
+ * @version 1.0.0
+ * @date 16/08/31
+ */
+public class Lambda5 {
+    public static void main(String... args) {
+
+        //BiConsumer Example
+        BiConsumer<String,Integer> printKeyAndValue
+                = (key,value) -> System.out.println(key+"-"+value);
+
+        printKeyAndValue.accept("One",1);
+        printKeyAndValue.accept("Two",2);
+
+        System.out.println("##################");
+
+        //Java Hash-Map foreach supports BiConsumer
+        HashMap<String, Integer> dummyValues = new HashMap<>();
+        dummyValues.put("One", 1);
+        dummyValues.put("Two", 2);
+        dummyValues.put("Three", 3);
+
+        dummyValues.forEach((key,value) -> System.out.println(key+"-"+value));
+
+    }
+}
+
+