利息计算

/**
 * 利息计算:
 * 借款 12000，一年还，名义月利息是 1.2%，名义年利息是 14.4%。
 * 即，每个月还款 1144
 * 12000 * 1.144 /12 = 1000 * 1.144 = 1144。
 * 实际月利率是多少？
 * @author zch
 * @date Nov 28, 2011
 *
 */

public class Lxjs {

	private static double test01(double x)
	{
		/**
		 * y1 * (1+x)    = 1144 
		 * y2 * (1+x)^2  = 1144 
		 * y3 * (1+x)^3  = 1144 
		 * y4 * (1+x)^4  = 1144 
		 * y5 * (1+x)^5  = 1144 
		 * y6 * (1+x)^6  = 1144 
		 * y7 * (1+x)^7  = 1144 
		 * y8 * (1+x)^8  = 1144 
		 * y9 * (1+x)^9  = 1144 
		 * y10* (1+x)^10 = 1144 
		 * y11* (1+x)^11 = 1144 
		 * y12* (1+x)^12 = 1144
		 * y1+...+y12 = 12000 
		 */

		double lxs[] = new double[12]; //利率
		double bjs[] = new double[12]; //本金
		double sum = 0;
		for(int i=0; i<12; i++)
		{
			lxs[i] = Math.pow(1+x, i+1);
			bjs[i] = 1144 / lxs[i];
			sum +=bjs[i];
			System.out.println( (i+1) + ":\t" +lxs[i] + ":\t" +bjs[i]);
		}
		return sum;

	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int i = 2100;
		for(; i<2200; i++)
		{
			System.out.println(i);
			double sum = test01(i/100000d);
			System.out.println(sum);
			if(sum<12000)
			{
				break;
			}
		}

	}

}

2132
1: 1.02132: 1120.1190616065485
2: 1.0430945424: 1096.7366365160267
3: 1.065333318043968: 1073.8423182900822
4: 1.0880462243846654: 1051.4259177242022
5: 1.1112433698885464: 1029.4774583129697
6: 1.1349350785345704: 1007.9871718099807
7: 1.1591318944089273: 986.9454938804497
8: 1.1838445863977256: 966.3430598445636
9: 1.2090841529797252: 946.1707005096969
10: 1.234861827121253: 926.4194380896259
11: 1.261189081275478: 907.0804822089316
12: 1.2880776324882712: 888.1452259908076
12000.692964783886
2133
1: 1.02133: 1120.1080943475663
2: 1.0431149689: 1096.7151599850845
3: 1.0653646111866373: 1073.8107761302265
4: 1.0880888383432483: 1051.3847396338367
5: 1.11129777326511: 1029.4270604347632
6: 1.1350017547688547: 1007.927957109615
7: 1.1592113421980745: 986.8778525154602
8: 1.1839373201271595: 966.2673695235234
9: 1.2091907031654718: 946.0873268419838
10: 1.2349827408639915: 926.3287349260119
11: 1.2613249227266206: 906.9827919732229
12: 1.2882289833283793: 888.0408800027641
11999.958743424058