- [x] done

src/main/java/com/github/hcsp/functional/RefactorToConsumer.java

@@ -23,47 +23,24 @@ public static void main(String[] args) {
     public static void printWithConsumer(
             Map<String, String> map1,
             Map<String, String> map2,
-            BiConsumer<String, String> consumer) {}
+            BiConsumer<String, String> consumer) {
+                map1.forEach(consumer);
+                map2.forEach(consumer);
+    }
 
-    public static void printWithComma(Map<String, String> map1, Map<String, String> map2) {
-        for (Map.Entry<String, String> entry : map1.entrySet()) {
-            String key = entry.getKey();
-            String value = entry.getValue();
-            System.out.println(key + "," + value);
-        }
+    static BiConsumer<Map<String, String>, Map<String, String>> printPrefix(String prefix) {
+        return ((map, map2) ->  printWithConsumer(map, map2, (k, v) -> System.out.println(k + prefix + v)));
+    }
 
-        for (Map.Entry<String, String> entry : map2.entrySet()) {
-            String key = entry.getKey();
-            String value = entry.getValue();
-            System.out.println(key + "," + value);
-        }
+    public static void printWithComma(Map<String, String> map1, Map<String, String> map2) {
+        printPrefix(",").accept(map1, map2);
     }
 
     public static void printWithDash(Map<String, String> map1, Map<String, String> map2) {
-        for (Map.Entry<String, String> entry : map1.entrySet()) {
-            String key = entry.getKey();
-            String value = entry.getValue();
-            System.out.println(key + "-" + value);
-        }
-
-        for (Map.Entry<String, String> entry : map2.entrySet()) {
-            String key = entry.getKey();
-            String value = entry.getValue();
-            System.out.println(key + "-" + value);
-        }
+        printPrefix("-").accept(map1, map2);
     }
 
     public static void printWithColon(Map<String, String> map1, Map<String, String> map2) {
-        for (Map.Entry<String, String> entry : map1.entrySet()) {
-            String key = entry.getKey();
-            String value = entry.getValue();
-            System.out.println(key + ":" + value);
-        }
-
-        for (Map.Entry<String, String> entry : map2.entrySet()) {
-            String key = entry.getKey();
-            String value = entry.getValue();
-            System.out.println(key + ":" + value);
-        }
+        printPrefix(":").accept(map1, map2);
     }
 }

src/main/java/com/github/hcsp/functional/RefactorToFunction.java

@@ -16,42 +16,30 @@ public static void main(String[] args) {
 
     // 请尝试将下列四个方法使用IntBinaryOperator进行重构，减少重复代码
     public static int[] calculate(int[] a, int[] b, IntBinaryOperator operator) {
-        return null;
+        int[] result = new int[a.length];
+        for (int i = 0; i < a.length; ++i) {
+            result[i] = operator.applyAsInt(a[i], b[i]);
+        }
+        return result;
     }
 
     // 将两个数组中的每个数字分别相加，然后返回相加后的数组。你可以假定传入的数组都是等长的
     // 下列minus/multiply/divide方法同理
     // 例如，a=[1, 2, 3], b=[4, 5, 6]
     // 返回 [5 (1+4), 7 (2+5), 9 (3+6)]
     public static int[] add(int[] a, int[] b) {
-        int[] result = new int[a.length];
-        for (int i = 0; i < a.length; ++i) {
-            result[i] = a[i] + b[i];
-        }
-        return result;
+        return calculate(a, b, Integer::sum);
     }
 
     public static int[] minus(int[] a, int[] b) {
-        int[] result = new int[a.length];
-        for (int i = 0; i < a.length; ++i) {
-            result[i] = a[i] - b[i];
-        }
-        return result;
+        return calculate(a, b, (x, y) -> x - y);
     }
 
     public static int[] multiply(int[] a, int[] b) {
-        int[] result = new int[a.length];
-        for (int i = 0; i < a.length; ++i) {
-            result[i] = a[i] * b[i];
-        }
-        return result;
+        return calculate(a, b, (x, y) -> x * y);
     }
 
     public static int[] divide(int[] a, int[] b) {
-        int[] result = new int[a.length];
-        for (int i = 0; i < a.length; ++i) {
-            result[i] = a[i] / b[i];
-        }
-        return result;
+        return calculate(a, b, (x, y) -> x / y);
     }
 }

src/main/java/com/github/hcsp/functional/RefactorToSupplier.java

@@ -1,8 +1,10 @@
 package com.github.hcsp.functional;
 
+import java.rmi.server.ObjID;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Random;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Supplier;
 
 public class RefactorToSupplier {
@@ -19,30 +21,23 @@ public static void main(String[] args) {
     // 请尝试使用函数式接口Supplier对三个方法进行重构，消除冗余代码
     // 并尽量尝试使用lambda表达式和方法引用来传递参数
     public static List<Object> create(Supplier<Object> supplier) {
-        return null;
-    }
-
-    public static List<Object> createObjects() {
         List<Object> result = new ArrayList<>();
         for (int i = 0; i < 10; i++) {
-            result.add(new Object());
+            result.add(supplier.get());
         }
         return result;
     }
 
+    public static List<Object> createObjects() {
+        return create(Object::new);
+    }
+
     public static List<Object> createStrings() {
-        List<Object> result = new ArrayList<>();
-        for (int i = 0; i < 10; i++) {
-            result.add("" + i);
-        }
-        return result;
+        AtomicInteger i = new AtomicInteger(0);
+        return create(() -> "" + i.getAndIncrement());
     }
 
     public static List<Object> createRandomIntegers() {
-        List<Object> result = new ArrayList<>();
-        for (int i = 0; i < 10; i++) {
-            result.add(randomInt());
-        }
-        return result;
+        return create(RefactorToSupplier::randomInt);
     }
 }