equation.java

数值分析算法源码(java) 这个学期一边学习java一边学习数值分析,因此用java写了一个数值分析算法的软件包numericalAnalysis. [说明] 适合使用者:会java的

package numericalAnalysis.equation;

import numericalAnalysis.function.Function;

/**
 * 本类包含了几个解方程的迭代方法.对照书:数值分析第二版,史万明等编,北京理工大学出版社
 * 
 * @author 山
 *
 */
public class Equation {
	private Function function;
	
	/**
	 * 新建一个方程.外部类中必须定义一个类实现Function接口,这个类的对象的f方法即方程f(x)=0的f(x).
	 * 
	 * @param function function的f(x)方法即方程f(x)=0的f(x)
	 */
	public Equation(Function function){
		this.function=function;
	}
	
	/**
	 * 用双点弦截法解方程.leftEndpoint相当于左端点a,rightEndpoint相当于右端点b.方程f(x)=0必须满足:
	 * 1.f(leftEndpoint)*f(rightEndpoint)<0
	 * 2.f'(x)不等于0,当x属于[leftEndpoint,rightEndpoint]时.
	 * 
	 * @param leftEndpoint 相当于左端点a
	 * @param rightEndpoint 相当于右端点b
	 * @return 方程的根
	 */
	public double getSolution(double leftEndpoint,double rightEndpoint){
		double x0 = leftEndpoint, x1 = rightEndpoint;

		do {
			x0 = (x0 * function.f(x1) - x1 * function.f(x0)) / (function.f(x1) - function.f(x0));
			x1 = (x1 * function.f(x0) - x0 * function.f(x1)) / (function.f(x0) - function.f(x1));
		} while (Math.abs(x1 - x0) > 1e-10);
		
		return x1;
	}
	
	/**
	 * 用双点弦截法解方程.leftEndpoint相当于左端点a,rightEndpoint相当于右端点b.方程f(x)=0必须满足:
	 * 1.f(leftEndpoint)*f(rightEndpoint)<0
	 * 2.f'(x)不等于0,当x属于[leftEndpoint,rightEndpoint]时.
	 * 
	 * @param leftEndpoint 相当于左端点a
	 * @param rightEndpoint 相当于右端点b
	 * @return 计算过程
	 */
	public String doubleChordSection(double leftEndpoint,double rightEndpoint){
		String output="\n";
		int count = 0;
		double x0 = leftEndpoint, x1 = rightEndpoint;

		do {
			output+="x" + count + "=" + x0 + ",		f(x" + (count++)
					+ ")=" + function.f(x0)+"\n";
			output+="x" + count + "=" + x1 + ",		f(x" + (count++)
					+ ")=" + function.f(x1)+"\n";
			x0 = (x0 * function.f(x1) - x1 * function.f(x0)) / (function.f(x1) - function.f(x0));
			x1 = (x1 * function.f(x0) - x0 * function.f(x1)) / (function.f(x0) - function.f(x1));
		} while (Math.abs(x1 - x0) > 1e-10);
		
		return output;
	}

}