count 实现

xiongyuxuan111 · xiongyuxuan111 · commit 7d6845df455d · 2019-03-11T16:59:45.000+08:00
diff --git a/src/main/java/stream/MyStream.java b/src/main/java/stream/MyStream.java
@@ -173,6 +173,11 @@ public T min(Comparator<T> comparator) {
         }
     }
 
+    @Override
+    public int count() {
+        return count(this.eval(),0);
+    }
+
     //===============================私有方法====================================
 
     /**
@@ -343,6 +348,18 @@ private static <T> T min(Comparator<T> comparator, MyStream<T> myStream, T min){
         }
     }
 
+    /**
+     * 递归函数 配合API.count
+     * */
+    private static <T> int count(MyStream<T> myStream, int count){
+        if(myStream.isEmptyStream()){
+            return count;
+        }
+
+        // count+1 进行递归
+        return count(myStream.eval(),count+1);
+    }
+
     /**
      * 当前流强制求值
      * @return 求值之后返回一个新的流
diff --git a/src/main/java/stream/Stream.java b/src/main/java/stream/Stream.java
@@ -80,6 +80,12 @@ public interface Stream<T> {
      * */
     T min(Comparator<T> comparator);
 
+    /**
+     * 计数 eval 强制求值
+     * @return  当前流的个数
+     * */
+    int count();
+
     /**
      * 返回空的 stream
      * @return 空stream
diff --git a/src/test/java/TestMyStream.java b/src/test/java/TestMyStream.java
@@ -17,7 +17,9 @@ public static void main(String[] args){
 
         intMyStream = intMyStream.distinct();
 
-        intMyStream.forEach(System.out::println);
+        System.out.println(intMyStream.count());
+
+//        intMyStream.forEach(System.out::println);
     }
 
     private static boolean idOdd(int num){

Original file line number	Diff line number	Diff line change
`@@ -17,7 +17,9 @@ public static void main(String[] args){`
`17`	`17`
`18`	`18`	`intMyStream = intMyStream.distinct();`
`19`	`19`
`20`		`- intMyStream.forEach(System.out::println);`
	`20`	`+ System.out.println(intMyStream.count());`
	`21`	`+`
	`22`	`+// intMyStream.forEach(System.out::println);`
`21`	`23`	`}`
`22`	`24`
`23`	`25`	`private static boolean idOdd(int num){`