From 26385313e2e4fabe70c06b2aa5e3d8a1b8df1a1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E2=80=9Cidpeng=E2=80=9D?= <630606938@qq.com>
Date: Tue, 31 Aug 2021 13:54:00 +0800
Subject: [PATCH 1/2] return filter(users, new Predicate<User>() {

---
 .../com/github/hcsp/polymorphism/User.java    | 67 ++++++++++++++-----
 1 file changed, 49 insertions(+), 18 deletions(-)

diff --git a/src/main/java/com/github/hcsp/polymorphism/User.java b/src/main/java/com/github/hcsp/polymorphism/User.java
index 51c95dc..0878c64 100644
--- a/src/main/java/com/github/hcsp/polymorphism/User.java
+++ b/src/main/java/com/github/hcsp/polymorphism/User.java
@@ -1,14 +1,19 @@
 package com.github.hcsp.polymorphism;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.function.Predicate;
 
 public class User {
-    /** 用户ID，数据库主键，全局唯一 */
+    /**
+     * 用户ID，数据库主键，全局唯一
+     */
     private final Integer id;
 
-    /** 用户名 */
+    /**
+     * 用户名
+     */
     private final String name;
 
     public User(Integer id, String name) {
@@ -24,40 +29,66 @@ public String getName() {
         return name;
     }
 
-    // 过滤ID为偶数的用户
-    public static List<User> filterUsersWithEvenId(List<User> users) {
+    public static List<User> filter(List<User> users, Predicate<User> predicate) {
         List<User> results = new ArrayList<>();
         for (User user : users) {
-            if (user.id % 2 == 0) {
+            if (predicate.test(user)) {
                 results.add(user);
             }
         }
         return results;
     }
 
+//    private interface 判断条件是否成立 {
+//        boolean 这个用户是否满足条件(User user);
+//    }
+
+//    private static class 判断id是不是偶数 implements 判断条件是否成立{
+//        @Override
+//        public boolean 这个用户是否满足条件(User user) {
+//            return user.id%2==0;
+//        }
+//    }
+
+    public static void main(String[] args) {
+        filterUsersWithEvenId(Arrays.asList(new User(1,"a"),new User(2,"b")));
+    }
+    // 过滤ID为偶数的用户
+    public static List<User> filterUsersWithEvenId(List<User> users) {
+        return filter(users, new Predicate<User>() {
+            @Override
+            public boolean test(User user) {
+                return user.id%2==0;
+            }
+        });
+    }
+
+
+
     // 过滤姓张的用户
     public static List<User> filterZhangUsers(List<User> users) {
-        List<User> results = new ArrayList<>();
-        for (User user : users) {
-            if (user.name.startsWith("张")) {
-                results.add(user);
+        return filter(users, new Predicate<User>() {
+            @Override
+            public boolean test(User user) {
+                return user.name.startsWith("张");
             }
-        }
-        return results;
+        });
     }
 
     // 过滤姓王的用户
     public static List<User> filterWangUsers(List<User> users) {
-        List<User> results = new ArrayList<>();
-        for (User user : users) {
-            if (user.name.startsWith("王")) {
-                results.add(user);
+        return filter(users, new Predicate<User>() {
+            @Override
+            public boolean test(User user) {
+                return user.name.startsWith("王");
             }
-        }
-        return results;
+        });
     }
+
     // 你可以发现，在上面三个函数中包含大量的重复代码。
     // 请尝试通过Predicate接口将上述代码抽取成一个公用的过滤器函数
     // 并简化上面三个函数
-    public static List<User> filter(List<User> users, Predicate<User> predicate) {}
+//    public static List<User> filter(List<User> users, Predicate<User> predicate) {
+//
+//    }
 }

From 0d610466352dfd6650538722f750fb2cb0f8cbe4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E2=80=9Cidpeng=E2=80=9D?= <630606938@qq.com>
Date: Tue, 31 Aug 2021 13:56:36 +0800
Subject: [PATCH 2/2] =?UTF-8?q?=E9=80=9A=E8=BF=87Predicate=E6=8E=A5?=
 =?UTF-8?q?=E5=8F=A3=E5=B0=86=E4=B8=8A=E8=BF=B0=E4=BB=A3=E7=A0=81=E6=8A=BD?=
 =?UTF-8?q?=E5=8F=96=E6=88=90=E4=B8=80=E4=B8=AA=E5=85=AC=E7=94=A8=E7=9A=84?=
 =?UTF-8?q?=E8=BF=87=E6=BB=A4=E5=99=A8=E5=87=BD=E6=95=B0?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/java/com/github/hcsp/polymorphism/User.java | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/main/java/com/github/hcsp/polymorphism/User.java b/src/main/java/com/github/hcsp/polymorphism/User.java
index 0878c64..6bdb24a 100644
--- a/src/main/java/com/github/hcsp/polymorphism/User.java
+++ b/src/main/java/com/github/hcsp/polymorphism/User.java
@@ -88,7 +88,5 @@ public boolean test(User user) {
     // 你可以发现，在上面三个函数中包含大量的重复代码。
     // 请尝试通过Predicate接口将上述代码抽取成一个公用的过滤器函数
     // 并简化上面三个函数
-//    public static List<User> filter(List<User> users, Predicate<User> predicate) {
-//
-//    }
+
 }