Check out example codes for "distance point to line java". It will help you in understanding the concepts better.

Code Example 1

//returns the distance between the infinite line(x1,y1)(x2,y2) and a point(x,y)
public float pDistance(float x, float y, float x1, float y1, float x2, float y2) {

      float A = x - x1; // position of point rel one end of line
      float B = y - y1;
      float C = x2 - x1; // vector along line
      float D = y2 - y1;
      float E = -D; // orthogonal vector
      float F = C;

      float dot = A * E + B * F;
      float len_sq = E * E + F * F;

      return (float) Math.abs(dot) / Math.sqrt(len_sq);
    }

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