import java.util.*;

public class Test {
    public static void main(String[] args) {
        int number = 9;
        int[] array = { -9,-8,-7,-6,-5,-4,-3,-2,-1,1, 2, 3, 4, 5, 6, 7, 8, 9 };
        List<String> list = f(number, array);
        for (String s : list)
            System.out.println(s);
    }

    static List<String> f(int number, int[] array) {
        List<String> list = new ArrayList<String>();
                // 这里先排除掉数组中与要找的数字相同的数，否则后面递归里面一直都在第一个循环中返回。这里不太好
        for (int i = 0; i < array.length; i++) 
            if(array[i] == number){
                list.add(number + "");
                array[i] = 0;
            }
                
        for (int i = 0; i < array.length; i++) {
            if (array[i] == number) {
                list.add(number + "");
                continue;
            }
            String s = g(i, number, array);
            if (!s.endsWith("null"))
                list.add(s);
        }
        return list;
    }

    static String g(int startIndex, int number, int[] array) {
        for (int i = startIndex; i < array.length; i++){
            if(array[i] == 0)
                continue;
            if (array[i] == number)
                return array[i] + "";
        }
        
        for (int i = startIndex; i < array.length; i++)
            if (array[i] < number) {
                number -= array[i];
                return array[i] + " + " + g(i + 1, number, array);
            }
        return null;
    }
}

------解决方案--------------------
package cn.gao.util.algorithm;
import java.util.ArrayList;
import java.util.Collection;
@SuppressWarnings("serial")
public class BagList extends ArrayList {
	@SuppressWarnings("unchecked")
	public BagList(int num)
	{
		super.add(num);	
	}
	@SuppressWarnings("unchecked")
	public BagList(Collection<Integer> collection,int num)
	{
		for(Integer o:collection)
		{		
			this.add(o);		
		}
		this.add(num);
	}
	@Override
	public boolean equals(Object arg0) {
		// TODO Auto-generated method stub
		if(arg0==this)
		{
			return true;		
		}
		if(arg0==null&&this!=null||this==null&&arg0!=null)
		{
			return false;		
		}
		if(arg0.getClass()!=BagList.class)
		{
			return false;
		}
		else{
			BagList b=(BagList)arg0;
			if(this.size()!=b.size())
			{
				return false;
				
			}
			for(Object o:b)
			{
				if(!this.contains(o))
				{
					return false;
				}	
			}
			return true;				
		}
	}
	@Override
	public int hashCode() {
		int sum=0;
		for(Object o:this)
		{
			sum+=(Integer)o;	
		}