side lengths of the quadriliateral is a,b,c,d

I know how to get the Perimeter, but i don't know how to write the code for the area...

Do i just need the side lengths? or do i also need angles?

 

 

public class Quadrilateral
{
    double a;
    double b;
    double c;
    double d;
    public Quadrilateral(){
        a=0;
        b=0;
        c=0;
        d=0;
    }
   
    public Quadrilateral (double q, double w, double e, double r){
        a=q;
        b=w;
        c=e;
        d=r;
}
   
public double getSideA(){
    return a;
}

public double getSideB(){
    return b;
}

public double getSideC(){
    return c;
}

public double getSideD(){
    return d;
}

public void setSideA(double q){
    a=q;
}

public void setSideB(double w){
    b=w;
}

public void setSideD(double r){
    d=r;
}

public void setSideA(double q){
    a=q;
  
}

public double Perimeter(double p){
    p=a+b+c+d;     
    return p;
    }

    public double Area(){
        return
    }
   
       public String toString(){
         return "Sides: " + a + b + c + d ;
    }