1.Main类
package s0223容器分拣存储;

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

public class Main {
	public static void main(String[] args) {

		String str = "this is a cat and that is a dog";
		String[] arry = str.split(" ");
		Map<String, Letter> letters = new HashMap<String, Letter>();
 
		
//		未优化代码
//		for (String temp : arry) {
//			if (!letters.containsKey(temp))// HashMap.containsKey() 判断map中是否有这个键
//			{
//				letters.put(temp, new Letter());
//
//			} else {
//				Letter col = letters.get(temp);// 根据key,返回value
//				col.setCount(col.getCount() + 1);
//			}
//		}
		
		//优化代码***********************************************************************************
		Letter col=null;
		for (String temp : arry) {
			if (null==(col=letters.get(temp)))// HashMap.containsKey() 判断map中是否有这个键
			{
				letters.put(temp, new Letter());

			} else {
				col.setCount(col.getCount() + 1);
			}
		}
		//优化代码***********************************************************************************
		
		letters.keySet().forEach(
				(element) -> System.out.println("字母" + element + "   次数:"+ letters.get(element).getCount())
				                );
	}
}

2.Letter类
package s0223容器分拣存储;

public class Letter {
 private String name;
 private int count;
 
 public Letter()
 {}

public Letter(String name, int count) {
	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;
}


}