Java SE入门及基础（50）& Java实现LinkedList（单向链表、双向链表）& Java实现栈

List 接口

1. 特性描述

A List is an ordered Collection (sometimes called a sequence). Lists may contain duplicate elements.

列表是有序的集合（有时称为序列）。 列表可能包含重复的元素。

The Java platform contains two general-purpose List implementations. ArrayList, which is usually the better-performing implementation, and LinkedList which offers better performance under certain circumstances.

Java 平台包含两个常用的 List 实现。 ArrayList 通常是性能较好的实现，而 LinkedList 在某些情况下可以提供更好的性能。

List 接口常用方法

E get ( int index ); // 获取给定位置的元素

E set ( int index , E element ); // 修改给定位置的元素

void add ( int index , E element ); // 在给定位置插入一个元素

E remove ( int index ); // 移除给定位置的元素

int indexOf ( Object o ); // 获取给定元素第一次出现的下标

int lastIndexOf ( Object o ); // 获取给定元素最后一次出现的下标

ListIterator < E > listIterator (); // 获取 List 集合专有的迭代器

ListIterator < E > listIterator ( int index ); // 获取 List 集合专有的迭代器，从给定的下标位置开始的迭代器

List < E > subList ( int fromIndex , int toIndex ); // 获取 List 集合的一个子集合

import java . util . ArrayList ;

import java . util . Iterator ;

import java . util . List ;

import java . util . ListIterator ;

public class ArrayListTest {

        public static void main ( String [] args ) {

        //集合有序是指存储顺序与遍历时取出来的顺序一致

        ArrayList < String > list = new ArrayList <> ();

        list . add ( "a" ); // 第一次调用 size =0;

        list . add ( "a" );

        list . add ( "b" );

        list . add ( "c" );

        list . add ( "d" );

        list . add ( 2 , "n" ); // a a b c d => a a b b c d => a a n b c d

        String old = list . set ( 1 , "g" );

        System . out . println ( old );

        System . out . println ( "====================" );

        for ( String str : list ){

                System . out . println ( str );

        }

        System . out . println ( "====================" );

        Iterator < String > iter = list . iterator ();

        while ( iter . hasNext ()){

                String s = iter . next ();

                System . out . println ( s );

        }

        System . out . println ( "====================" );

        ListIterator < String > listIterator = list . listIterator ();

        while ( listIterator . hasNext ()){

                String s = listIterator . next ();

                System . out . println ( s );

        }

        System . out . println ( "====================" );

        ListIterator < String > prevIterator = list . listIterator ( list . size ());

        while ( prevIterator . hasPrevious ()){

                String s = prevIterator . previous ();

                System . out . println ( s );

        }

        System . out . println ( "====================" );

        List < String > subList = list . subList ( 2 , 4 );

        for ( String str : subList ){

                System . out . println ( str );

        }

        System . out . println ( "====================" );

        int size = list . size ();

        for ( int i = 0 ; i < size ; i ++ ){

                String s = list . get ( i );

                System . out . println ( s );

        }

        System . out . println ( "===================" );

        ArrayList < Integer > numbers = new ArrayList <> ();

        numbers . add ( 1 );

        numbers . add ( 2 );

        numbers . add ( 3 );

        numbers . add ( 4 );

        //移除下标为 3 这个位置的元素

        numbers . remove ( 3 ); // 这是移除下标为 3 这个位置的元素还是移除 3 这个元素？

        //移除 3 这个元素

        numbers . remove (( Integer ) 3 );

        for ( Integer number : numbers ){

                System . out . println ( number );

        }

        numbers . add ( 2 );

        numbers . add ( 2 );

        int index1 = numbers . indexOf ( 2 );

        int index2 = numbers . lastIndexOf ( 2 );

        System . out . println ( index1 );

        System . out . println ( index2 );

        }

}

package com . wq . list ;

/**

* 自定义单向链表

* @param <T> 泛型变量

*/

public class MyNode < T > {

        private T data ; // 链中存储的数据

        private MyNode < T > next ; // 下一个链

        public MyNode ( T data , MyNode < T > next ) {

                this . data = data ;

                this . next = next ;

        }

        public T getData () {

                return data ;

        }

        public void setData ( T data ) {

                this . data = data ;

        }

        public MyNode < T > getNext () {

                return next ;

        }

        public void setNext ( MyNode < T > next ) {

                this . next = next ;

        }

}

package com . wq . list ;

public class MyNodeTest {

        public static void main ( String [] args ) {

                MyNode < String > first = new MyNode <> ( " 第一个链 " , null );

                MyNode < String > second = new MyNode <> ( " 第二个链 " , null );

                first . setNext ( second );

                MyNode < String > third = new MyNode <> ( " 第三个链 " , null );

                second . setNext ( third );

                MyNode < String > fourth = new MyNode <> ( " 第四个链 " , null );

                third . setNext ( fourth );

                MyNode < String > nextNode = first ;

                while ( nextNode != null ){

                        System . out . println ( nextNode . getData ());

                        nextNode = nextNode . getNext ();

                }

                System . out . println ( "===================" );

                MyNode < Integer > number4 = new MyNode <> ( 4 , null );

                MyNode < Integer > number3 = new MyNode <> ( 3 , number4 );

                MyNode < Integer > number2 = new MyNode <> ( 2 , number3 );

                MyNode < Integer > number1 = new MyNode <> ( 1 , number2 );

                MyNode < Integer > next = number1 ;

                while ( next != null ){

                        System . out . println ( next . getData ());

                        next = next . getNext ();

                }

        }

}

双向链表

package com . wq . list ;

/**

* 自定义双向链表

* @param <T>

*/

public class DeNode < T > {

        private T data ; // 链中存储的数据

        private DeNode < T > prev ; // 前一个链

        private DeNode < T > next ; // 后一个链

        public DeNode ( T data , DeNode < T > prev , DeNode < T > next ) {

                this . data = data ;

                this . prev = prev ;

                this . next = next ;

        }

        public T getData () {

                return data ;

        }

        public void setData ( T data ) {

                this . data = data ;

        }

        public DeNode < T > getPrev () {

                return prev ;

        }

        public void setPrev ( DeNode < T > prev ) {

                this . prev = prev ;

        }

        public DeNode < T > getNext () {

                return next ;

        }

        public void setNext ( DeNode < T > next ) {

                this . next = next ;

        }

}

package com . wq . list ;

public class DeNodeTest {

        public static void main ( String [] args ) {

                DeNode < Integer > number1 = new DeNode <> ( 1 , null , null );

                DeNode < Integer > number2 = new DeNode <> ( 2 , number1 , null );

                number1 . setNext ( number2 );

                DeNode < Integer > number3 = new DeNode <> ( 3 , number2 , null );

                number2 . setNext ( number3 );

                DeNode < Integer > number4 = new DeNode <> ( 4 , number3 , null );

                number3 . setNext ( number4 );

                DeNode < Integer > nextNode = number1 ;

                while ( nextNode != null ){

                        System . out . println ( nextNode . getData ());

                        nextNode = nextNode . getNext ();

                }

                System . out . println ( "==================" );

                DeNode < Integer > prevNode = number4 ;

                while ( prevNode != null ){

                        System . out . println ( prevNode . getData ());

                        prevNode = prevNode . getPrev ();

                }

        }

}

package com . wq . list ;

import java . util . LinkedList ;

public class LinkedListTest {

        public static void main ( String [] args ) {

                LinkedList < String > list = new LinkedList <> ();

                list . add ( " 第一个字符串 " );

                list . add ( " 第二个字符串 " );

                list . addLast ( " 第三个字符串 " );

                list . addFirst ( " 第四个字符串 " );

                String first = list . removeFirst (); // 将第一个链移除

                String last = list . removeLast (); // 将最后一个链移除

                System . out . println ( first );

                System . out . println ( last );

                first = list . getFirst ();

                last = list . getLast ();

                System . out . println ( first );

                System . out . println ( last );

        }

}

package com . wq . list ;

import java . util . ArrayList ;

/**

* 自定义栈：后进先出

*/

public class MyStack < T > extends ArrayList < T > {

        public void push ( T t ){

                add ( t );

        }

        public T pop (){

                if ( size () == 0 ) throw new IllegalArgumentException ( " 栈里没有数据啦 " );

                        T t = get ( size () - 1 );

                        remove ( t );

                        return t ;

        }

}

package com .wq . list ;

public class MyStackTest {

        public static void main ( String [] args ) {

                MyStack < Integer > stack = new MyStack <> ();

                stack . push ( 1 );

                stack . push ( 2 );

                stack . push ( 3 );

                stack . push ( 4 );

                stack . push ( 5 );

                while ( ! stack . isEmpty ()){

                        System . out . println ( stack . pop ());

                }

        }

}

package com . wq . list ;

import java . io . * ;

import java . util . ArrayList ;

import java . util . List ;

import java . util . Scanner ;

/**

* 从控制台录入 5 位学生信息：姓名，性别，年龄，成绩，并将这些学生信息以 "," 衔接起来，

* 然后存储至文本中。然后再从文本中将这些信息读取至集合中。

*/

public class Exercise {

        public static void main ( String [] args ) {

                List < Student > students = new ArrayList <> ();

                Scanner sc = new Scanner ( System . in );

                for ( int i = 0 ; i < 5 ; i ++ ){

                        System . out . println ( " 请输入姓名： " );

                        String name = sc . next ();

                        System . out . println ( " 请输入性别： " );

                        String sex = sc . next ();

                        System . out . println ( " 请输入年龄： " );

                        int age = sc . nextInt ();

                        System . out . println ( " 请输入成绩： " );

                        double score = sc . nextDouble ();

                        students . add ( new Student ( name , sex , age , score ));

                }

                saveStudents ( students , "F:\\stu\\stu.txt" );

                List < Student > read = readStudents ( "F:\\stu\\stu.txt" );

                for ( Student stu : read ){

                        System . out . println ( stu );

                }

        }

        public static List < Student > readStudents ( String path ){

                List < Student > students = new ArrayList <> ();

                try ( FileReader reader = new FileReader ( path );

                        BufferedReader br = new BufferedReader ( reader );){

                        String line ;

                        while (( line = br . readLine ()) != null ){

                                String [] arr = line . split ( "," );

                                //name + "," + sex +"," + age + "," + score;

                                String name = arr [ 0 ];

                                String sex = arr [ 1 ];

                                int age = Integer . parseInt ( arr [ 2 ]); // Float.parseFloat()

                                double score = Double . parseDouble ( arr [ 3 ]);

                                students . add ( new Student ( name , sex , age , score ));

                        }

                } catch ( FileNotFoundException e ) {

                        e . printStackTrace ();

                } catch ( IOException e ) {

                        e . printStackTrace ();

                }

                return students ;

        }

        public static void saveStudents ( List < Student > students , String path ){

                File file = new File ( path );

                File parent = file . getParentFile ();

                if ( ! parent . exists ()) parent . mkdirs ();

                        try ( FileWriter writer = new FileWriter ( file );

                                BufferedWriter bw = new BufferedWriter ( writer );){

                                for ( Student stu : students ){

                                        bw . write ( stu . toString ());

                                        bw . newLine ();

                                }

                                bw . flush ();

                        } catch ( IOException e ) {

                                e . printStackTrace ();

                        }

                }

}

Java SE文章参考:Java SE入门及基础知识合集-CSDN博客