binary search tree - Java implementation of BST delete node -

i'm trying make method delete node in bst , not working..i'm using node class made myself.. tried debugging didnt on addressing error in code.

appreciate on how make work.

public boolean delete(node z) {     if (z == null)         return false;      node x,y;     if( z.getleft() == null || z.getright()== null)         y = z;     else {          y = (node) successor(z);     }     if (y.getleft() != null)         x = y.getleft();     else x = y.getright();     if(x != null)         x.setparent(y.getparent());     if(y.getparent() == null) {         this.node=x;     }     else if (y == y.getparent().getleft())     {             y.getparent().setleft(x);     }         else y.getparent().setright(x);      if(y==z)         z.setkey(y.getkey());     return true;     }   public node treeminimum(node x) {     while (x.getleft() != null)         x = x.getleft();      return x; }  public node successor(node node) {     node x = node;      if (x.getright() != null)         return treeminimum(x.getright());      node y = x.getparent();     while (y != null && x == y.getright()) {         x = y;         y = y.getparent();     }      return y; } 

// here complete solution public void delete(final integer data) {     root = delete(root, data); }  public node<oinfo> delete(node<oinfo> node, final integer data) {     if (node == null) {         return null;     }      int cmp = data.compareto(new integer(node.getdata().data));     if (cmp < 0) {         node.setleft(delete(node.getleft(), data));     } else if (cmp > 0) {         node.setright(delete(node.getright(), data));     } else {         boolean isroot = false;         if (root == node) {             isroot = true;         }         if (node.getleft() == null) {             return node.getright();         }         if (node.getright() == null) {             return node.getleft();         }         node<oinfo> t = node;         node = findminimum(t.getright());         node.setright(deletemin(t.getright()));         node.setleft(t.getleft());         if (isroot) {             root = node;         }     }      return node; }  private node<oinfo> deletemin(node<oinfo> node) { if (node.getleft() == null) {     return node.getright();     } node.setleft(deletemin(node.getleft())); return node; }  private node<oinfo> findminimum(node<oinfo> node) { if (node == null) {     throw new illegalargumentexception("null value of node provided."); }  if (node.getleft() == null) {     return node; } else {     return findminimum(node.getleft()); } }