用 Java 求解积分
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Solve an Integral in Java
提问by dafero
I need to develop a program in Java to solve some integrals. Integrals like this:
我需要用 Java 开发一个程序来解决一些积分问题。像这样的积分：
I've looked for some functions to do this, in java.Math but I didn't find anything.
我在 java.Math 中寻找了一些函数来做到这一点，但我没有找到任何东西。
Has anyone an idea to get a solution for this? (Maybe some extra libraries or something like that).
有没有人想解决这个问题？（也许是一些额外的库或类似的东西）。
采纳答案by adamse
The Wikipedia article on Numerical Integration has a section on methods for one-dimensional integrals.
维基百科关于数值积分的文章有一节介绍一维积分的方法。
You should have no problem implementing the "trapezoidal" or "rectangle" rule.
实施“梯形”或“矩形”规则应该没有问题。
回答by Will A
Check out Simpson's Ruleon Wikipedia.
查看维基百科上的辛普森规则。
回答by Greg Hewgill
The Apache Commons Mathlibrary contains, in the Numerical Analysissection, four different numerical integrators:
- Romberg's method
- Simpson's method
- trapezoid method
- Legendre-Gauss method
- 罗姆伯格的方法
- 辛普森的方法
- 梯形法
- 勒让德-高斯方法
回答by jiji
/*------------------------------------------------------------------------------------------------------
* Small program that numerically calculates an integral according to
* Simpson's algorithm. Before executing it, you must enter:
* - the expression of the function f: line 12;
* - the lower and upper limits b of the integral: lines 39 and 40;
* - the number of measurements n (n is integer !!!): line 41.
*------------------------------------------------------------------------------------------------------*/
// Class function: Defines Simpson's rule
class Function{
// Define the function to integrate
double f (double x) {
return Math.Cos(x);
}
// Simpson's method for integral calculus
// a = lower bound
// b = upper bound of integration
// n = number of passes (higher = less margin of error, but takes longer)
double IntSimpson(double a, double b,int n){
int i,z;
double h,s;
n=n+n;
s = f(a)*f(b);
h = (b-a)/n;
z = 4;
for(i = 1; i<n; i++){
s = s + z * f(a+i*h);
z = 6 - z;
}
return (s * h)/3;
}
}
class integration{
// Class result: calculates the integral and displays the result.
public static void main(String args[]){
// Call class function
Function function;
function = new Function();
// ENTER the desired values of a, b and n !!!
double a = ???? ;
double b = ???? ;
int n = ???? ;
// Applies simpson method to function
double result = function.IntSimpson(a,b,n);
// Show results
System.out.println("Integral is: " + result);
}
}
