0 课程地址
https://coding.imooc.com/lesson/207.html#mid=13709
1 重点关注
1.1 使用二叉树实现映射Map
详见3.1用二叉树实现映射Map
2 课程内容
3 Coding
3.1 使用二叉树实现映射Map
- 需求
使用二叉树实现的映射统计 傲慢与偏见 书的英文词汇量
- Map接口
package com.company;
public interface Map<K,V> {
/**
* 是否为空
* @author weidoudou
* @date 2022/12/26 17:50
* @return boolean
**/
boolean isEmpty();
/**
* 获取元素个数
* @author weidoudou
* @date 2022/12/26 17:51
* @return int
**/
int getSize();
/**
* 是否包含
* @author weidoudou
* @date 2022/12/26 17:52
* @param key 请添加参数描述
* @return boolean
**/
boolean contains(K key);
/**
* 获取元素
* @author weidoudou
* @date 2022/12/26 17:59
* @param key 请添加参数描述
* @return V
**/
V get(K key);
/**
* 新增元素
* @author weidoudou
* @date 2022/12/26 17:53
* @param key 请添加参数描述
* @param value 请添加参数描述
* @return void
**/
void add(K key,V value);
/**
* 修改元素
* @author weidoudou
* @date 2022/12/26 17:54
* @param key 请添加参数描述
* @param value 请添加参数描述
* @return void
**/
void set(K key,V value);
/**
* 删除元素
* @author weidoudou
* @date 2022/12/26 17:55
* @param key 请添加参数描述
* @return V
**/
V remove(K key);
}
- BSTMap
package com.company; import java.util.ArrayList; public class Main { /*public static void main(String[] args) { ArrayList<String> words = new ArrayList<>(); if(FileOperation.readFile("pride-and-prejudice.txt",words)){ System.out.println("total words is "+words.size()); } Map<String,Integer> map = new LinkedListMap<>(); for(String word : words){ if(map.contains(word)){ map.set(word,map.get(word)+1); }else{ map.add(word,1); } } System.out.println("different words is "+map.getSize()); System.out.println("pride size is"+map.get("pride")); System.out.println("prejudice size is"+map.get("prejudice")); // write your code here }*/ public static void main(String[] args) { ArrayList<String> words = new ArrayList<>(); if(FileOperation.readFile("pride-and-prejudice.txt",words)){ System.out.println("total words is "+words.size()); } Map<String,Integer> map = new BSTMap<>(); for(String word : words){ if(map.contains(word)){ map.set(word,map.get(word)+1); }else{ map.add(word,1); } } System.out.println("different words is "+map.getSize()); System.out.println("pride size is"+map.get("pride")); System.out.println("prejudice size is"+map.get("prejudice")); // write your code here } }
- 文件处理类：
package com.company;
import java.io.FileInputStream;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.Locale;
import java.io.File;
import java.io.BufferedInputStream;
import java.io.IOException;
// 文件相关操作
public class FileOperation {
// 读取文件名称为filename中的内容，并将其中包含的所有词语放进words中
public static boolean readFile(String filename, ArrayList<String> words){
if (filename == null || words == null){
System.out.println("filename is null or words is null");
return false;
}
// 文件读取
Scanner scanner;
try {
File file = new File(filename);
if(file.exists()){
FileInputStream fis = new FileInputStream(file);
scanner = new Scanner(new BufferedInputStream(fis), "UTF-8");
scanner.useLocale(Locale.ENGLISH);
}
else
return false;
}
catch(IOException ioe){
System.out.println("Cannot open " + filename);
return false;
}
// 简单分词
// 这个分词方式相对简陋, 没有考虑很多文本处理中的特殊问题
// 在这里只做demo展示用
if (scanner.hasNextLine()) {
String contents = scanner.useDelimiter("\\A").next();
int start = firstCharacterIndex(contents, 0);
for (int i = start + 1; i <= contents.length(); )
if (i == contents.length() || !Character.isLetter(contents.charAt(i))) {
String word = contents.substring(start, i).toLowerCase();
words.add(word);
start = firstCharacterIndex(contents, i);
i = start + 1;
} else
i++;
}
return true;
}
// 寻找字符串s中，从start的位置开始的第一个字母字符的位置
private static int firstCharacterIndex(String s, int start){
for( int i = start ; i < s.length() ; i ++ )
if( Character.isLetter(s.charAt(i)) )
return i;
return s.length();
}
}
- 测试类：
package com.company; import java.util.ArrayList; public class Main { /*public static void main(String[] args) { ArrayList<String> words = new ArrayList<>(); if(FileOperation.readFile("pride-and-prejudice.txt",words)){ System.out.println("total words is "+words.size()); } Map<String,Integer> map = new LinkedListMap<>(); for(String word : words){ if(map.contains(word)){ map.set(word,map.get(word)+1); }else{ map.add(word,1); } } System.out.println("different words is "+map.getSize()); System.out.println("pride size is"+map.get("pride")); System.out.println("prejudice size is"+map.get("prejudice")); // write your code here }*/ public static void main(String[] args) { ArrayList<String> words = new ArrayList<>(); if(FileOperation.readFile("pride-and-prejudice.txt",words)){ System.out.println("total words is "+words.size()); } Map<String,Integer> map = new BSTMap<>(); for(String word : words){ if(map.contains(word)){ map.set(word,map.get(word)+1); }else{ map.add(word,1); } } System.out.println("different words is "+map.getSize()); System.out.println("pride size is"+map.get("pride")); System.out.println("prejudice size is"+map.get("prejudice")); // write your code here } }
- 测试结果：
total words is 125901
different words is 6530
pride size is53
prejudice size is11
Process finished with exit code 0
速度快很多
诸葛
