Subtraction
Write the test:
    public void testSubtract() {
 
        Complex z1 = new Complex(1, 1);
        Complex z2 = new Complex(1, 1);
        Complex z3 = z1.subtract(z2);
        assertEquals(0, z3.getRealPart(), tolerance);
        assertEquals(0, z3.getImaginaryPart(), tolerance);
  
    }    Implement the feature:
    public Complex subtract(Complex z) {
        // ???? Auto-generated method stub
        return null;
    }Debug until the test passes:
    public Complex subtract(Complex z) {
        return new Complex(this.real - z.real, this.imaginary - z.imaginary);
    }