您可以在此处使用GridBagLayout而不是使用null布局：

GridBagConstraints gridBagConstraints;

panel = new JPanel();

findLabel = new javax.swing.JLabel();

findField = new javax.swing.JTextField();

replaceLabel = new javax.swing.JLabel();

replaceField = new javax.swing.JTextField();

replaceAllButton = new javax.swing.JButton();

replaceButton = new javax.swing.JButton();

setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

panel.setLayout(new GridBagLayout());

findLabel.setText("Find :");

gridBagConstraints = new GridBagConstraints();

gridBagConstraints.ipadx = 94;

gridBagConstraints.ipady = 30;

panel.add(findLabel, gridBagConstraints);

gridBagConstraints = new GridBagConstraints();

gridBagConstraints.ipadx = 149;

panel.add(findField, gridBagConstraints);

replaceLabel.setText("Replace With :");

gridBagConstraints = new GridBagConstraints();

gridBagConstraints.gridx = 0;

gridBagConstraints.gridy = 1;

gridBagConstraints.ipadx = 34;

gridBagConstraints.ipady = 23;

panel.add(replaceLabel, gridBagConstraints);

gridBagConstraints = new GridBagConstraints();

gridBagConstraints.gridx = 1;

gridBagConstraints.gridy = 1;

gridBagConstraints.ipadx = 149;

panel.add(replaceField, gridBagConstraints);

replaceAllButton.setText("Find And Replace All");

gridBagConstraints = new GridBagConstraints();

gridBagConstraints.gridx = 0;

gridBagConstraints.gridy = 2;

gridBagConstraints.ipady = 9;

panel.add(replaceAllButton, gridBagConstraints);

replaceButton.setText("Replace");

gridBagConstraints = new GridBagConstraints();

gridBagConstraints.gridx = 1;

gridBagConstraints.gridy = 2;

gridBagConstraints.ipadx = 99;

gridBagConstraints.ipady = 8;

panel.add(replaceButton, gridBagConstraints);

//adding panel to the jframe

getContentPane().add(panel, BorderLayout.CENTER);

pack();