JAVASE入门十脚-红黑树,比较器,泛型

红黑树Set,ArrayList数组,LinkedList链表

AVL二叉树

 红黑树

插入节点一般是红色

treeSet()底层是treeMap,利用红黑树来实现

package ContainerDemo1;import java.util.Objects;public class PersonDemo {private  String name;private int age;public PersonDemo(){}public PersonDemo(int age, String name) {this.age = age;this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;PersonDemo that = (PersonDemo) o;return age == that.age && Objects.equals(name, that.name);}@Overridepublic int hashCode() {return Objects.hash(name, age);}@Overridepublic String toString() {return "PersonDemo{" +"name='" + name + '\'' +", age=" + age +'}';}
}package ContainerDemo1;import java.util.HashSet;public class TestDemoo {public static void main(String[] args) {HashSet hashSet=new HashSet();PersonDemo personDemo=new PersonDemo(15,"张三");PersonDemo personDemo1=new PersonDemo(16,"li三");PersonDemo personDemo2=new PersonDemo(15,"张三");hashSet.add(personDemo);hashSet.add(personDemo1);hashSet.add(personDemo2);System.out.println(hashSet);}
}

 1、set中存放的是无序,唯一的数据
2.set不可以通过下标获取对应位置的元素的值,因为无序的特点
3、使用treeset底层的实现是treemap,利用红黑树来进行实现
4、设置元素的时候,如果是自定义对象,会直找对象中的equals和hashcode的方法,如果没有,比较的
5、树中的元素是要默认进行排序操作的,如果是基本数据类型,下动比较,如果是引用类型的话,需要
比较器分类:
内部比较器
定义在元素的类中,通过实现comparable接口来进行实现
外部比较器
定义在当前类中,通过实现comparator接口来实现,但是要将该比较器传递到集合中

注意:外部比较器可以定义建一个工具类。此时所有而要比较的规则如果致的话,可以复用,
内部比较器只有在存储当前对象的时候才可以使用

当两者同时用的时候使用外部比较器

TreeSet定义内部比较器;

package ContainerDemo1;import java.util.Objects;public class PersonDemo implements Comparable{private  String name;private int age;public PersonDemo(){}public PersonDemo(int age, String name) {this.age = age;this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;PersonDemo that = (PersonDemo) o;return age == that.age && Objects.equals(name, that.name);}@Overridepublic int hashCode() {return Objects.hash(name, age);}@Overridepublic String toString() {return "PersonDemo{" +"name='" + name + '\'' +", age=" + age +'}';}/*此比较器按照name的长度来比较*/@Overridepublic int compareTo(Object o) {PersonDemo personDemo=(PersonDemo)o;if(personDemo.name.length()>this.name.length()){return 1;}else if(personDemo.name.length()<this.name.length()){return -1;}else {return 0;}}}package ContainerDemo1;import java.util.HashSet;
import java.util.TreeSet;public class TestDemoo {public static void main(String[] args) {TreeSet treeSet=new TreeSet();PersonDemo personDemo=new PersonDemo(15,"张三");PersonDemo personDemo1=new PersonDemo(16,"li三");PersonDemo personDemo2=new PersonDemo(15,"张三");treeSet.add(personDemo);treeSet.add(personDemo1);treeSet.add(personDemo2);System.out.println(treeSet);}}

外部比较器:

package ContainerDemo1;import java.util.Comparator;
import java.util.HashSet;
import java.util.TreeSet;public class TestDemoo implements Comparator<PersonDemo> {public static void main(String[] args) {TreeSet treeSet=new TreeSet(new TestDemoo());PersonDemo personDemo=new PersonDemo(15,"张三");PersonDemo personDemo1=new PersonDemo(16,"li三");PersonDemo personDemo2=new PersonDemo(15,"张三");treeSet.add(personDemo);treeSet.add(personDemo1);treeSet.add(personDemo2);System.out.println(treeSet);}@Overridepublic int compare(PersonDemo o1, PersonDemo o2) {if(o1.getAge()>o2.getAge()){return -1;}else if(o1.getAge()<o2.getAge()){return 1;}else {return 0;}}
}package ContainerDemo1;import java.util.Objects;public class PersonDemo /*implements Comparable*/{private  String name;private int age;public PersonDemo(){}public PersonDemo(int age, String name) {this.age = age;this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;PersonDemo that = (PersonDemo) o;return age == that.age && Objects.equals(name, that.name);}@Overridepublic int hashCode() {return Objects.hash(name, age);}@Overridepublic String toString() {return "PersonDemo{" +"name='" + name + '\'' +", age=" + age +'}';}/*此比较器按照name的长度来比较*/
//    @Override
//    public int compareTo(Object o) {
//        PersonDemo personDemo=(PersonDemo)o;
//        if(personDemo.name.length()>this.name.length()){
//            return 1;
//        }
//        else if(personDemo.name.length()<this.name.length()){
//            return -1;
//        }
//        else {
//        return 0;}
//
//    }}

泛型

package ContainerDemo1;import java.util.ArrayList;
import java.util.List;public class ModernDemo {public static void main(String[] args) {List<String> list=new ArrayList<String>();list.add("415");list.add("撒");list.add("555");list.add(new Dog("455","123").toString());System.out.println(list);for(String ite:list){System.out.println(ite);}}
}

当做一些集合的统一操作的时候,需要保证集合的类型是统的,此时需要泛型来进行限制
优点:
1、数据安全
2、获取数据时效率比较高
给集合中的元素没置相同的类型就是泛型的基本需求
使用:
在定义对象的时候,通过 中没置合理的类型来进行实现

泛型类

package ContainerDemo1;public class FanXingClass<A> {
private int id;
private A a;public int getId() {return id;}public void setId(int id) {this.id = id;}public A getA() {return a;}public void setA(A a) {this.a = a;}public void show(){System.out.println(id+","+a);}
}package ContainerDemo1;public class FanXingDemo {public static void main(String[] args) {FanXingClass<String> fanXing=new FanXingClass<String>();fanXing.setA("机");fanXing.setId(55);fanXing.show();}}