Question

我在类中声明了专用的Complex变量“ root”。我在void方法“ iterate”中将root的值设置为复数

我希望打印'root'的新值（第60行），但是当我尝试时，它将打印为null。因此，我认为这不是正确的“根”。

我的代码：

class Newton {

public static final int MAXITER = 20;
public static final double TOL = 1.0e-10;


private Polynomial f;        //Polynomial
private Polynomial fp;      //Derivative of the polynomial

private Complex root;
private int numIterations;
private int err;


//Basic constructor. Calculate and set fp in this method.

public Newton(Polynomial p) {
  this.f = p;
  this.fp = p.derivative();
}

// Newton-Rapshon method



public void iterate(Complex z0) {
      Complex[] z = new Complex[MAXITER];
      z[0] = z0;
        for(int i = 0 ; i<MAXITER ; i++){
        if(fp.evaluate(z[i]).abs() <= TOL){
          this.err = -1;
          return;
        }
      z[i+1] = z[i].add((f.evaluate(z[i])).divide(fp.evaluate(z[i])));
        if(f.evaluate(z[i]).abs() != TOL){
          this.err = -2;
          return;
      } if (f.evaluate(z[i]).abs() <= TOL){
          this.err = 0;
          this.root = z[i];
          this.numIterations = i;
          return;
      }
    }}

    // Tester function.
    public static void main(String[] args) {
        // Basic tester: find a root of f(z) = z^3-1 from the starting point
        // z_0 = 1+i.
        Complex[] coeff = new Complex[] { new Complex(-1.0,0.0), new Complex(),
                                          new Complex(), new Complex(1.0,0.0) };
        Polynomial p    = new Polynomial(coeff);
        Newton     n    = new Newton(p);

    Complex z0 = new Complex(1.0,1.0);
        n.iterate(z0);
        System.out.println(n.root);
    }}

Answer 1

您需要在git pull https://github.com/someuser/someproject.git类中为root创建一个吸气剂，因为它是一个私有字段。

Newton

然后，您可以使用吸气剂代替尝试访问class Newton { public static final int MAXITER = 20; public static final double TOL = 1.0e-10; private Polynomial f; //Polynomial private Polynomial fp; //Derivative of the polynomial private Complex root; private int numIterations; private int err; //Basic constructor. Calculate and set fp in this method. public Newton(Polynomial p) { this.f = p; this.fp = p.derivative(); } public Complex getRoot(){ return this.root; } }（即，使用n.root代替newtonObj.getRoot()）

newtonObj.root

我在方法内更改了变量，如何访问更改后的变量？

1 个答案: