采用Map容器 统计每个单词出现的次数

  package cn.bjsxt.map;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * this is a cat and that is a mice and where is the food?
 * 统计每个单词出现的次数
 * 
 * 存储到Map中
 * key :String 
 * value:自定义类型
 * 
 * "分拣" 思路
 * 1、为所有key创建容器
 *    之后容器中存放对应value
 * 2、第一次创建容器，并存放值value
 *    第二次之后，直接使用容器存放值
 * @author Administrator
 *
 */
public class Demo01 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String str ="this is a cat and that is a mice and where is the food";
		//分割字符串
		String[] strArray=str.split(" ");
		//存储到Map中
		Map<String,Letter>  letters = new HashMap<String,Letter>();   
		for(String temp:strArray){			
			/*
			 //1、为所有key创建容器		 
			if(!letters.containsKey(temp)){
				Letter col = new Letter();
				col.setCount(1); //第一次值存放容器中
				letters.put(temp, col);//组成键值对
			}else{
				//2、	 第二次之后，直接使用容器存放值
				Letter col =letters.get(temp); //直接使用容器
				col.setCount(col.getCount()+1);
			}*/
			Letter col = null;
			if(null==(col=letters.get(temp))){
				col = new Letter();
				col.setCount(1); //第一次值存放容器中
				letters.put(temp, col);
			}else{
				//2、	 第二次之后，直接使用容器存放值				
				col.setCount(col.getCount()+1);
			}
		}
		//输出Map的值
		Set<String> keys = letters.keySet();
		for(String key:keys){
			Letter col =letters.get(key);
			System.out.println("字母:"+key+",次数"+col.getCount());
		} 
		
		
	}
	public static void test1(){
		String str ="this is a cat and that is a mice and where is the food";
		//分割字符串
		String[] strArray=str.split(" ");
		//存储到Map中
		Map<String,Letter>  letters = new HashMap<String,Letter>();
		/*
		for(String temp:strArray){
			
			 //1、为所有key创建容器
			 	 之后容器中存放对应value
			 
			if(!letters.containsKey(temp)){
				letters.put(temp, new Letter());
			}
		}
		for(String temp:strArray){
			
			//  容器中存放对应value
			
			Letter col =letters.get(temp); //直接使用容器
			col.setCount(col.getCount()+1);
		}
		
		*/
		for(String temp:strArray){
			
			 //1、为所有key创建容器		 
			if(!letters.containsKey(temp)){
				letters.put(temp, new Letter());
			}
			//2、	 之后容器中存放对应value
			Letter col =letters.get(temp); //直接使用容器
			col.setCount(col.getCount()+1);
		}
		
		//输出Map的值
		Set<String> keys = letters.keySet();
		for(String key:keys){
			Letter col =letters.get(key);
			System.out.println("字母:"+key+",次数"+col.getCount());
		}
	}
}

package cn.bjsxt.map;

public class Letter {
	private String name;
	private int count;
	public Letter() {
		// TODO Auto-generated constructor stub
	}
	public Letter(String name, int count) {
		super();
		this.name = name;
		this.count = count;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getCount() {
		return count;
	}
	public void setCount(int count) {
		this.count = count;
	}
	
	
	
}

实例2

package cn.bjsxt.map;

import java.util.ArrayList;
import java.util.List;

/**
 * 班级
 * @author Administrator
 *
 */
public class ClassRoom {
	private String no;
	private List<Student> stus; //学生列表
	private double total; //总分
	public ClassRoom() {
		stus = new ArrayList<Student>();	
	}
	
	public ClassRoom(String no) {
		this();    //构造器没有相互调用  该构造器未初始化
		this.no = no;	
	}
	public String getNo() {
		return no;
	}
	public void setNo(String no) {
		this.no = no;
	}
	public List<Student> getStus() {
		return stus;
	}
	public void setStus(List<Student> stus) {
		this.stus = stus;
	}
	public double getTotal() {
		return total;
	}
	public void setTotal(double total) {
		this.total = total;
	}
	
	

package cn.bjsxt.map;

public class Student {
	private String name;
	private String no;
	private double score;
	public Student() { 
	}
	public Student(String name, String no, double score) {
		super();
		this.name = name;
		this.no = no;
		this.score = score;
	}

	public String getName() {
		return name;
	}

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

	public String getNo() {
		return no;
	}

	public void setNo(String no) {
		this.no = no;
	}

	public double getScore() {
		return score;
	}

	public void setScore(double score) {
		this.score = score;
	}

	@Override
	public String toString() {
		return "Student [name=" + name + ", no=" + no + ", score=" + score
				+ "]";
	}

}

package cn.bjsxt.map;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * 定义一个Student类,属性:name 姓名,classNumber 班号,score 成绩
   现在将若干Student对象放入List,请统计出每个班级的总分和平均分,分别打印出来
 以面向对象的思维解决
 * @author Administrator
 *
 */
public class MapDemo03 {
	public static void main(String[] args) {
		List<Student> list = new ArrayList<Student>();
		exam(list);		
		
		//统计		
		Map<String,ClassRoom> rooms = new HashMap<String,ClassRoom>();
		count(rooms,list);
		//打印
		printScore(rooms);
	}
	
	/**
	 * 打印 总分与平均分
	 */
	public static void printScore(Map<String,ClassRoom> rooms){
		Set<Map.Entry<String,ClassRoom>> entrySet =rooms.entrySet();
		Iterator<Map.Entry<String,ClassRoom>> it =entrySet.iterator();
		while(it.hasNext()){
			Map.Entry<String,ClassRoom> entry =it.next();
			ClassRoom room = entry.getValue();
			double avg = room.getTotal()/room.getStus().size();
			System.out.println("班号为:"+room.getNo()+",总分"+room.getTotal()+",平均分"+avg);
		}		
	}
	
	
	/**
	 * 统计分数
	 */
	public static void count(Map<String,ClassRoom> rooms,List<Student> list){
		for(Student stu:list){
			String no = stu.getNo();
			double score = stu.getScore();
			//根据班级编号 查看  Map是否存在该班级  分拣思路
			ClassRoom room = rooms.get(no);
			if(null==room){  //第一次
				room = new ClassRoom(no);
				rooms.put(no, room);
			}			
			//存储 总分
			room.setTotal(room.getTotal()+score);
			room.getStus().add(stu); //加入学生			
		}
	}
	
	
	/**
	 * 现在将若干Student对象放入List
	 * @param list
	 */
	public static void exam(List<Student> list){
		list.add(new Student("a","001",80));
		list.add(new Student("b","001",80));
		list.add(new Student("a","002",80));
		list.add(new Student("c","003",80));
		list.add(new Student("d","003",80));
	}
}