Feature.java

package ruc.irm.classification;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * 文档的特征
 * 
 * @author xiatian
 *
 */
public class Feature {
	/** 每个关键词在不同类别中出现的文档数量 */
	private Map<String, Integer> docCountMap = new HashMap<String, Integer>();
	/** 特征名称 */
	private String name;
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public void incDocCount(String category){
		if(docCountMap.containsKey(category)){
			docCountMap.put(category, docCountMap.get(category)+1);
		}else{
			docCountMap.put(category, 1);
		}
	}
	public int getDocCount(String category){
		if(docCountMap.containsKey(category)){
			return docCountMap.get(category);
		}else{
			return 0;
		}
	}
	
	public void write(DataOutput out) throws IOException{
		out.writeUTF(name==null?"":name);
		
		out.writeInt(docCountMap.size());
		for(String category:docCountMap.keySet()){
			out.writeUTF(category);
			out.writeInt(docCountMap.get(category));
		}
	}
	
	public void readFields(DataInput in) throws IOException {
		this.name = in.readUTF();
		
		docCountMap = new HashMap<String, Integer>();
		int size = in.readInt();
		for(int i=0; i<size; i++){
			String category = in.readUTF();
			int docCount = in.readInt();
			docCountMap.put(category, docCount);
		}
	}
	
	public static Feature read(DataInput in) throws IOException{
		Feature f = new Feature();
		f.readFields(in);
		return f;
	}

}