İf statement, Code not work . Please

final EditText yaz = (EditText)findViewById(R.id.editText);
    final Button bas = (Button)findViewById(R.id.button);

    yaz.setText("500");
        bas.setOnClickListener(new View.OnClickListener() {
                                        @Override
                                        public void onClick(View v) {
                                            String afd = yaz.getText().toString();
                                            if (afd == "1000") {
                                                yaz.setText("2000");
                                            }
                                        }
                                    }
    );

    }