学习笔记，仅供参考
因为我突然懒了，所以这个Blog以代码为主，解释为辅
文章目录
集合去除ArrayList中重复的字符串元素去除ArrayList中重复的自定义对象元素LinkedList的特有功能集合
去除ArrayList中重复的字符串元素
package com.guiyang.object;import java.util.ArrayList;import java.util.Iterator;@SuppressWarnings({"rawtypes", "unchecked" })public class Demo1_ArrayList {public static void main(String[] args) {ArrayList alist = new ArrayList();alist.add("a");alist.add("a");alist.add("a");alist.add("b");alist.add("b");alist.add("c");ArrayList newlist = getSingle(alist);System.out.println(newlist);}public static ArrayList getSingle(ArrayList list) {ArrayList newlist = new ArrayList();Iterator iterator = list.iterator();while (iterator.hasNext()) {Object object = iterator.next();if (!newlist.contains(object)) {newlist.add(object);}}return newlist;}}
输出：
[a, b, c]
去除ArrayList中重复的自定义对象元素
注意，contains方法判断集合中是否包含某个元素，底层依赖的是equals方法。
所以，在进行定义对象的比较时，我们需要改写自定义类的equals方法.
自定义Person类：
package com.guiyang.bean;public class Person {private String name;private int age;public Person() {super();}public Person(String name, int age) {super();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;}@Overridepublic String toString() {return "Person [name=" + name + ", age=" + age + "]";}@Overridepublic boolean equals(Object obj) {Person p = (Person)obj;return this.name.equals(p.name) && this.age == p.age;}}
Java:
package com.guiyang.restudy3;import java.util.ArrayList;import java.util.Iterator;import com.guiyang.bean.Person;@SuppressWarnings({"rawtypes", "unchecked"})public class D2ArrayListRepeat {public static void main(String[] args) {ArrayList list = new ArrayList();//创建集合对象list.add(new Person("小白", 23));list.add(new Person("小白", 23));list.add(new Person("大黄", 24));list.add(new Person("大黄", 24));list.add(new Person("王子", 24));ArrayList newList = getSingle(list);//调用方法去除重复System.out.println(newList);}public static ArrayList getSingle(ArrayList list) {ArrayList newList = new ArrayList<>();//1,创建新集合Iterator it = list.iterator();//2,根据传入的集合(老集合)获取迭代器while(it.hasNext()) {//3,遍历老集合Object obj = it.next();//记录住每一个元素if(!newList.contains(obj)) {//如果新集合中不包含老集合中的元素newList.add(obj); //将该元素添加}}return newList;}}
输出：
[Person [name=小白, age=23], Person [name=大黄, age=24], Person [name=王子, age=24]]
同样，remove方法移除集合中的某个元素时，底层依赖的还是equals方法。
package com.guiyang.restudy3;import java.util.ArrayList;import java.util.Iterator;import com.guiyang.bean.Person;@SuppressWarnings({"rawtypes", "unchecked"})public class D2ArrayListRepeat {public static void main(String[] args) {ArrayList list = new ArrayList();//创建集合对象list.add(new Person("小白", 23));list.add(new Person("小白", 23));list.add(new Person("大黄", 24));list.add(new Person("大黄", 24));list.add(new Person("王子", 24));list.remove(new Person("王子", 24));System.out.println(list);}public static ArrayList getSingle(ArrayList list) {ArrayList newList = new ArrayList<>();//1,创建新集合Iterator it = list.iterator();//2,根据传入的集合(老集合)获取迭代器while(it.hasNext()) {//3,遍历老集合Object obj = it.next(); //记录住每一个元素if(!newList.contains(obj)) {//如果新集合中不包含老集合中的元素newList.add(obj); //将该元素添加}}return newList;}}
输出：
[Person [name=小白, age=23], Person [name=小白, age=23], Person [name=大黄, age=24], Person [name=大黄, age=24]]
LinkedList的特有功能
package com.guiyang.restudy3;import java.util.LinkedList;@SuppressWarnings({"rawtypes", "unchecked" })public class D1Linkedlist {public static void main(String[] args) {LinkedList list = new LinkedList();list.addFirst("a");list.addFirst("b");list.addFirst("c");list.addFirst("d");list.addLast("e");list.addLast("f");System.out.println(list.getFirst());System.out.println(list.getLast());System.out.println(list.removeFirst());System.out.println(list.removeLast());System.out.println("---------");System.out.println(list.get(0));System.out.println(list);}}
输出：
dfdf---------c[c, b, a, e]
