update

Author: deleiguo

doc/jdk/src/java/util/LinkedList.md

@@ -173,16 +173,14 @@ public E getLast() {
 
 /** 查找相应位置的 Node 对象 */
 Node<E> node(int index) {
- 	// size >> 1 每次最坏情况下遍历链表中一半的元素
+ 	// size >> 1 每次最好的情况下只需遍历链表中一半的元素
   if (index < (size >> 1)) {
-    // 如果下标小于元素数量的一半
     Node<E> x = first;
     // 从first开始遍历
     for (int i = 0; i < index; i++)
       x = x.next;
     return x;
   } else {
-    // 如果小标不小于元素数量的一半
     Node<E> x = last;
     // 从last开始遍历
     for (int i = size - 1; i > index; i--)

source/java/interview/src/main/java/cn/delei/java/util/HashSetDemo.java

@@ -0,0 +1,36 @@
+package cn.delei.java.util;
+
+import cn.delei.pojo.Person;
+import cn.delei.util.PrintUtil;
+
+import java.util.HashSet;
+
+/**
+ * HashSet Demo
+ *
+ * @author deleiguo
+ */
+public class HashSetDemo {
+    public static void main(String[] args) {
+        add();
+    }
+
+    static void add() {
+        HashSet<Integer> hashSet = new HashSet<>();
+        hashSet.add(null);
+        hashSet.add(1);
+        hashSet.add(2);
+        hashSet.add(1);
+        hashSet.add(null);
+        hashSet.add(10);
+        hashSet.forEach(System.out::println);
+        PrintUtil.printDivider();
+        HashSet<Person> personHashSet = new HashSet<>();
+        
+        personHashSet.add(new Person("deleiguo", 28, "111111"));
+        personHashSet.add(new Person("deleiguo", 28, "222222"));
+        personHashSet.add(new Person("delei", 28, "222222"));
+        personHashSet.add(new Person("guo", 28, "111111"));
+        personHashSet.forEach(System.out::println);
+    }
+}

source/java/interview/src/main/java/cn/delei/java/util/LinkedListDemo.java

@@ -8,13 +8,56 @@
 
 /**
  * java.util.LinkedList
+ *
  * @author deleiguo
  */
 public class LinkedListDemo {
 
     public static LinkedList<Integer> dataList = new LinkedList<>();
+
     public static void main(String[] args) {
-        opera();
+//        add();
+        get();
+//        opera();
+    }
+
+
+    static void add() {
+        StopWatch stopWatch = new StopWatch();
+        stopWatch.start("add");
+        final int size = 10;
+        dataList = new LinkedList<>();
+        // 头插
+        for (int i = 0; i < size; i++) {
+            dataList.addFirst(i);
+        }
+        // 尾插
+        for (int i = 0; i < size; i++) {
+            dataList.add(i + 10);
+        }
+        System.out.println(dataList);
+
+        stopWatch.stop();
+        System.out.println(stopWatch.prettyPrint());
+    }
+
+    static void get() {
+        StopWatch stopWatch = new StopWatch();
+
+        final int size = 100000;
+        dataList = new LinkedList<>();
+        // 头插
+        for (int i = 0; i < size; i++) {
+            dataList.add(i);
+        }
+        stopWatch.start("index < (size>>1)");
+        System.out.println(dataList.get(size / 2 - 50));
+        stopWatch.stop();
+
+        stopWatch.start("index > (size>>1)");
+        System.out.println(dataList.get(size / 2 + 50));
+        stopWatch.stop();
+        System.out.println(stopWatch.prettyPrint());
     }
 
     /**

source/java/interview/src/main/java/cn/delei/pojo/Person.java

@@ -1,6 +1,8 @@
 package cn.delei.pojo;
 
 import java.io.Serializable;
+import java.util.Objects;
+import java.util.Optional;
 
 /**
  * POJO 类
@@ -60,4 +62,28 @@ public String toString() {
                 ", password='" + password + '\'' +
                 '}';
     }
+
+    @Override
+    public int hashCode() {
+        int nameHash = name.toUpperCase().hashCode();
+        return nameHash ^ age;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (Objects.isNull(obj)) {
+            return false;
+        }
+        if (this == obj) {
+            return true;
+        }
+
+        if (obj instanceof Person) {
+            final Person p = (Person) obj;
+            return this.getName().equals(p.getName())
+                    && this.getAge() == p.getAge();
+        }
+
+        return false;
+    }
 }

source/java/interview/src/main/java/cn/delei/pojo/Teacher.java

@@ -1,6 +1,7 @@
 package cn.delei.pojo;
 
 import java.io.Serializable;
+import java.util.Objects;
 
 /**
  * POJO 类：老师
@@ -17,7 +18,8 @@ public class Teacher implements Serializable {
      */
     private int age;
 
-    public Teacher(){}
+    public Teacher() {
+    }
 
     public Teacher(String name, int age) {
         this.name = name;
@@ -47,4 +49,26 @@ public String toString() {
                 ", age=" + age +
                 '}';
     }
+
+    @Override
+    public int hashCode() {
+        int nameHash = name.toUpperCase().hashCode();
+        return nameHash ^ age;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (Objects.isNull(obj)) {
+            return false;
+        }
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof Teacher) {
+            final Teacher p = (Teacher) obj;
+            return p.getName().equals(this.getName())
+                    && p.getAge() == this.getAge();
+        }
+        return false;
+    }
 }