Java Day 17

Vector
 addElement()
 elements()
  hasMoreElements()
  nextElement()

LinkedList
 addFirst()
 addLast()

 获取不移除
 getFirst() 有异常抛出
 peekFirst() 返回null

 获取并移除
 removeFirst()  有异常抛出
 pollFirst() 返回null

ArrayList
 

package com.company.Day017;

import java.util.LinkedList;

/**
 * Created by junius on 2016/10/6.
 */
public class DuiLie {
    private LinkedList link;
    DuiLie(){
        link = new LinkedList();
    }
    public void myAdd(Object obj){
        link.addLast(obj);
    }
    public Object myGet(){
        return link.removeFirst();
    }
    public boolean isNull(){
        return link.isEmpty();
    }
}
/*--------------------------------------------*/
package com.company.Day017;
import com.company.Day017.DuiLie;
/**
 * Created by junius on 2016/10/6.
 */
public class DuiLieDemo {
    public static void main(String[] args){
        DuiLie dl = new DuiLie();
        dl.myAdd("abc1");
        dl.myAdd("abc2");
        dl.myAdd("abc3");
        dl.myAdd("abc4");

        while(!dl.isNull()){
            System.out.println(dl.myGet());
        }
    }
}

Set
 HashSet 内部数据结构是哈希表，不同步
  判断哈希值 hashCode()
  判断内容 equals()
 TreeSet

package com.company.Day017;

import java.util.HashSet;
import java.util.Iterator;

/**
 * Created by junius on 2016/10/7.
 */
public class HashSetTest {
    public static void main(String[] args) {
        HashSet hs = new HashSet();

        hs.add(new Person("lisi1", 23));
        hs.add(new Person("lisi2", 24));
        hs.add(new Person("lisi3", 25));
        hs.add(new Person("lisi1", 23));

        Iterator it = hs.iterator();
        while (it.hasNext()) {
            Person p = (Person) it.next();
            System.out.println(p.getName() + "..." + p.getAge());
        }
    }
}

去除ArrayList重复元素

package com.company.Day017;

import java.sql.Array;
import java.sql.SQLSyntaxErrorException;
import java.util.ArrayList;
import java.util.Iterator;

/**
 * Created by junius on 2016/10/7.
 */
public class removeArrayList {
    public static void main(String[] args){
        ArrayList al = new ArrayList();
        al.add("abc1");
        al.add("abc2");
        al.add("abc3");
        al.add("abc1");
        al.add("abc");
        System.out.println(al);
        al = getSingleArrayList(al);
        System.out.println(al);
    }

    public static ArrayList getSingleArrayList(ArrayList al) {
        ArrayList temp = new ArrayList();
        Iterator it = al.iterator();
        while(it.hasNext()){
            Object obj = it.next();
            if(!temp.contains(obj))
                temp.add(obj);
        }
        return temp;
    }
}

LinkedHashSet 有序的HashSet

TreeSet
 对Set元素进行排序，不同步
 判断元素的唯一性。就是比较方法
 实现Comparable接口 覆盖compareTo方法

package com.company.Day017;

import java.util.Comparator;

/**
 * Created by junius on 2016/10/7.
 */


public class Person implements Comparable{
    private String name;
    private int age;

    public Person() {
    }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public int hashCode() {
        return this.name.hashCode()+age;
    }

    @Override
    public boolean equals(Object obj) {
        Person p = (Person)obj;
        return this.name.equals(p.name) && this.age==p.age;
    }

    @Override
    public int compareTo(Object o) {
        Person p = (Person) o;
        int temp = this.age - p.age;
        return temp==0?this.name.compareTo(p.name):temp;
    }
}

Comparator比较器
 如果不按照对象中具备的自然顺序进行排序，或对象中不具备自然顺序。
 可以使用TreeSet集合第二种排序方法，让集合自身具备比较功能。
 定义一个类实现Comparator接口，覆盖compare方法。
 将该类对象作为参数传递给TreeSet集合的构造函数

package com.company.Comparator;

import com.company.Day017.Person;

import java.util.Comparator;

/**
 * Created by junius on 2016/10/7.
 */
public class ComparatorByName implements Comparator{
    @Override
    public int compare(Object o1, Object o2) {
        Person p1 = (Person) o1;
        Person p2 = (Person) o2;

        int temp = p1.getName().compareTo(p2.getName());
        return temp==0?p1.getAge()-p2.getAge():temp;
//        return -1;
    }
}

package com.company.Day017;

import com.company.Comparator.ComparatorByLength;

import java.util.Iterator;
import java.util.TreeSet;

/**
 * Created by junius on 2016/10/7
 */
public class TreeSetUsing {
    public static void main(String[] args) {
        TreeSet ts = new TreeSet(new ComparatorByLength());

        ts.add("abd");
        ts.add("abccc");
        ts.add("abc");
        ts.add("zzzz");
        ts.add("aaaa");

        Iterator it = ts.iterator();
        while (it.hasNext()) {
            String s = (String) it.next();
            System.out.println(s);
        }
    }
}

二叉树
 1、实现怎么存进去怎么取出来

 compare 直接 return 1;

2、逆序取元素

compare 直接 return -1;

 
字符串长度排序-TreeSet

package com.company.Comparator;

import java.util.Comparator;

/**
 * Created by junius on 2016/10/7.
 */
public class ComparatorByLength implements Comparator{
    @Override
    public int compare(Object o1, Object o2) {
        String s1 = (String)o1;
        String s2 = (String)o2;
        int temp = s1.length()-s2.length();
        return temp==0?s1.compareTo(s2):temp;
    }
}

/*------------------------------------------------------------*/
package com.company.Day017;

import com.company.Comparator.ComparatorByLength;

import java.util.Iterator;
import java.util.TreeSet;

/**
 * Created by junius on 2016/10/7
 */
public class TreeSetUsing {
    public static void main(String[] args) {
        TreeSet ts = new TreeSet(new ComparatorByLength());

        ts.add("abd");
        ts.add("abccc");
        ts.add("abc");
        ts.add("zzzz");
        ts.add("aaaa");

        Iterator it = ts.iterator();
        while (it.hasNext()) {
            String s = (String) it.next();
            System.out.println(s);
        }
    }
}