Erro na calculadora - Java

Boa Noite. eu estou com um erro na minha calculadora já tentei de tudo mais não sei por que ela não calcula quem poder ajudar eu agradeço.

Codigo:
package Interface;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

public class Calculadora extends javax.swing.JFrame {

ScriptEngineManager sem = new ScriptEngineManager();
ScriptEngine se = sem.getEngineByName("JavaScript");

public Calculadora() {
    initComponents();
    setLocationRelativeTo(null);
}

@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jPanel1 = new javax.swing.JPanel();
    txtOperacoes = new javax.swing.JLabel();
    txtResultado = new javax.swing.JLabel();
    jPanel2 = new javax.swing.JPanel();
    btnIgual = new javax.swing.JButton();
    btnNove = new javax.swing.JButton();
    btnPotencia = new javax.swing.JButton();
    btnPorcentagem = new javax.swing.JButton();
    btnDivisao = new javax.swing.JButton();
    btnMutiplicacao = new javax.swing.JButton();
    btnMenos = new javax.swing.JButton();
    btnMais = new javax.swing.JButton();
    btnApagar = new javax.swing.JButton();
    btnSete = new javax.swing.JButton();
    btnOito = new javax.swing.JButton();
    btnQuatro = new javax.swing.JButton();
    btnCinco = new javax.swing.JButton();
    btnSeis = new javax.swing.JButton();
    btnUm = new javax.swing.JButton();
    btnDois = new javax.swing.JButton();
    btnTres = new javax.swing.JButton();
    btnZero = new javax.swing.JButton();
    btnPonto = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setResizable(false);
    getContentPane().setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());

    jPanel1.setBackground(new java.awt.Color(244, 253, 251));
    jPanel1.setForeground(new java.awt.Color(244, 253, 251));
    jPanel1.setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());

    txtOperacoes.setFont(new java.awt.Font("Roboto", 1, 18)); // NOI18N
    txtOperacoes.setForeground(new java.awt.Color(55, 62, 71));
    txtOperacoes.setHorizontalAlignment(javax.swing.SwingConstants.RIGHT);
    jPanel1.add(txtOperacoes, new org.netbeans.lib.awtextra.AbsoluteConstraints(10, 50, 310, 40));

    txtResultado.setFont(new java.awt.Font("Roboto Light", 1, 48)); // NOI18N
    txtResultado.setForeground(new java.awt.Color(55, 62, 71));
    txtResultado.setHorizontalAlignment(javax.swing.SwingConstants.RIGHT);
    jPanel1.add(txtResultado, new org.netbeans.lib.awtextra.AbsoluteConstraints(10, 80, 310, 59));

    getContentPane().add(jPanel1, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 0, 330, 160));

    jPanel2.setBackground(new java.awt.Color(255, 255, 255));
    jPanel2.setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());

    btnIgual.setFont(new java.awt.Font("Roboto", 0, 30)); // NOI18N
    btnIgual.setForeground(new java.awt.Color(255, 255, 255));
    btnIgual.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn3.png"))); // NOI18N
    btnIgual.setText("=");
    btnIgual.setFocusPainted(false);
    btnIgual.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnIgual.setPreferredSize(new java.awt.Dimension(50, 50));
    btnIgual.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn3.png"))); // NOI18N
    btnIgual.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn3_press.png"))); // NOI18N
    btnIgual.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnIgualActionPerformed(evt);
        }
    });
    jPanel2.add(btnIgual, new org.netbeans.lib.awtextra.AbsoluteConstraints(260, 340, -1, -1));

    btnNove.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnNove.setForeground(new java.awt.Color(55, 62, 71));
    btnNove.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnNove.setText("9");
    btnNove.setFocusPainted(false);
    btnNove.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnNove.setMaximumSize(new java.awt.Dimension(20, 20));
    btnNove.setMinimumSize(new java.awt.Dimension(20, 20));
    btnNove.setPreferredSize(new java.awt.Dimension(50, 50));
    btnNove.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnNove.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnNove.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnNoveActionPerformed(evt);
        }
    });
    jPanel2.add(btnNove, new org.netbeans.lib.awtextra.AbsoluteConstraints(180, 100, -1, -1));

    btnPotencia.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnPotencia.setForeground(new java.awt.Color(55, 62, 71));
    btnPotencia.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnPotencia.setText("^");
    btnPotencia.setFocusPainted(false);
    btnPotencia.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnPotencia.setMaximumSize(new java.awt.Dimension(100, 20));
    btnPotencia.setMinimumSize(new java.awt.Dimension(100, 20));
    btnPotencia.setPreferredSize(new java.awt.Dimension(50, 50));
    btnPotencia.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnPotencia.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnPotencia.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnPotenciaActionPerformed(evt);
        }
    });
    jPanel2.add(btnPotencia, new org.netbeans.lib.awtextra.AbsoluteConstraints(100, 20, -1, -1));

    btnPorcentagem.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnPorcentagem.setForeground(new java.awt.Color(55, 62, 71));
    btnPorcentagem.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnPorcentagem.setText("%");
    btnPorcentagem.setFocusPainted(false);
    btnPorcentagem.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnPorcentagem.setPreferredSize(new java.awt.Dimension(50, 50));
    btnPorcentagem.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnPorcentagem.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnPorcentagem.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnPorcentagemActionPerformed(evt);
        }
    });
    jPanel2.add(btnPorcentagem, new org.netbeans.lib.awtextra.AbsoluteConstraints(180, 20, -1, -1));

    btnDivisao.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnDivisao.setForeground(new java.awt.Color(55, 62, 71));
    btnDivisao.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnDivisao.setText("÷");
    btnDivisao.setFocusPainted(false);
    btnDivisao.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnDivisao.setPreferredSize(new java.awt.Dimension(50, 50));
    btnDivisao.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnDivisao.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnDivisao.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnDivisaoActionPerformed(evt);
        }
    });
    jPanel2.add(btnDivisao, new org.netbeans.lib.awtextra.AbsoluteConstraints(260, 20, -1, -1));

    btnMutiplicacao.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnMutiplicacao.setForeground(new java.awt.Color(55, 62, 71));
    btnMutiplicacao.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnMutiplicacao.setText("x");
    btnMutiplicacao.setFocusPainted(false);
    btnMutiplicacao.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnMutiplicacao.setPreferredSize(new java.awt.Dimension(50, 50));
    btnMutiplicacao.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnMutiplicacao.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnMutiplicacao.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnMutiplicacaoActionPerformed(evt);
        }
    });
    jPanel2.add(btnMutiplicacao, new org.netbeans.lib.awtextra.AbsoluteConstraints(260, 100, -1, -1));

    btnMenos.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnMenos.setForeground(new java.awt.Color(55, 62, 71));
    btnMenos.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnMenos.setText("-");
    btnMenos.setFocusPainted(false);
    btnMenos.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnMenos.setPreferredSize(new java.awt.Dimension(50, 50));
    btnMenos.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnMenos.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnMenos.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnMenosActionPerformed(evt);
        }
    });
    jPanel2.add(btnMenos, new org.netbeans.lib.awtextra.AbsoluteConstraints(260, 180, -1, -1));

    btnMais.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnMais.setForeground(new java.awt.Color(55, 62, 71));
    btnMais.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnMais.setText("+");
    btnMais.setFocusPainted(false);
    btnMais.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnMais.setPreferredSize(new java.awt.Dimension(50, 50));
    btnMais.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnMais.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnMais.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnMaisActionPerformed(evt);
        }
    });
    jPanel2.add(btnMais, new org.netbeans.lib.awtextra.AbsoluteConstraints(260, 260, -1, -1));

    btnApagar.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnApagar.setForeground(new java.awt.Color(55, 62, 71));
    btnApagar.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnApagar.setText("C");
    btnApagar.setFocusPainted(false);
    btnApagar.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnApagar.setMaximumSize(new java.awt.Dimension(20, 20));
    btnApagar.setMinimumSize(new java.awt.Dimension(20, 20));
    btnApagar.setPreferredSize(new java.awt.Dimension(50, 50));
    btnApagar.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnApagar.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnApagar.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnApagarActionPerformed(evt);
        }
    });
    jPanel2.add(btnApagar, new org.netbeans.lib.awtextra.AbsoluteConstraints(20, 20, -1, -1));

    btnSete.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnSete.setForeground(new java.awt.Color(55, 62, 71));
    btnSete.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnSete.setText("7");
    btnSete.setFocusPainted(false);
    btnSete.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnSete.setMaximumSize(new java.awt.Dimension(20, 20));
    btnSete.setMinimumSize(new java.awt.Dimension(20, 20));
    btnSete.setPreferredSize(new java.awt.Dimension(50, 50));
    btnSete.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnSete.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnSete.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnSeteActionPerformed(evt);
        }
    });
    jPanel2.add(btnSete, new org.netbeans.lib.awtextra.AbsoluteConstraints(20, 100, -1, -1));

    btnOito.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnOito.setForeground(new java.awt.Color(55, 62, 71));
    btnOito.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnOito.setText("8");
    btnOito.setFocusPainted(false);
    btnOito.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnOito.setMaximumSize(new java.awt.Dimension(20, 20));
    btnOito.setMinimumSize(new java.awt.Dimension(20, 20));
    btnOito.setPreferredSize(new java.awt.Dimension(50, 50));
    btnOito.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnOito.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnOito.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnOitoActionPerformed(evt);
        }
    });
    jPanel2.add(btnOito, new org.netbeans.lib.awtextra.AbsoluteConstraints(100, 100, -1, -1));

    btnQuatro.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnQuatro.setForeground(new java.awt.Color(55, 62, 71));
    btnQuatro.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnQuatro.setText("4");
    btnQuatro.setFocusPainted(false);
    btnQuatro.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnQuatro.setMaximumSize(new java.awt.Dimension(20, 20));
    btnQuatro.setMinimumSize(new java.awt.Dimension(20, 20));
    btnQuatro.setPreferredSize(new java.awt.Dimension(50, 50));
    btnQuatro.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnQuatro.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnQuatro.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnQuatroActionPerformed(evt);
        }
    });
    jPanel2.add(btnQuatro, new org.netbeans.lib.awtextra.AbsoluteConstraints(20, 180, -1, -1));

    btnCinco.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnCinco.setForeground(new java.awt.Color(55, 62, 71));
    btnCinco.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnCinco.setText("5");
    btnCinco.setFocusPainted(false);
    btnCinco.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnCinco.setMaximumSize(new java.awt.Dimension(20, 20));
    btnCinco.setMinimumSize(new java.awt.Dimension(20, 20));
    btnCinco.setPreferredSize(new java.awt.Dimension(50, 50));
    btnCinco.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnCinco.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnCinco.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnCincoActionPerformed(evt);
        }
    });
    jPanel2.add(btnCinco, new org.netbeans.lib.awtextra.AbsoluteConstraints(100, 180, -1, -1));

    btnSeis.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnSeis.setForeground(new java.awt.Color(55, 62, 71));
    btnSeis.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnSeis.setText("6");
    btnSeis.setFocusPainted(false);
    btnSeis.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnSeis.setMaximumSize(new java.awt.Dimension(20, 20));
    btnSeis.setMinimumSize(new java.awt.Dimension(20, 20));
    btnSeis.setPreferredSize(new java.awt.Dimension(50, 50));
    btnSeis.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnSeis.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnSeis.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnSeisActionPerformed(evt);
        }
    });
    jPanel2.add(btnSeis, new org.netbeans.lib.awtextra.AbsoluteConstraints(180, 180, -1, -1));

    btnUm.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnUm.setForeground(new java.awt.Color(55, 62, 71));
    btnUm.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnUm.setText("1");
    btnUm.setFocusPainted(false);
    btnUm.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnUm.setMaximumSize(new java.awt.Dimension(20, 20));
    btnUm.setMinimumSize(new java.awt.Dimension(20, 20));
    btnUm.setPreferredSize(new java.awt.Dimension(50, 50));
    btnUm.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnUm.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnUm.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnUmActionPerformed(evt);
        }
    });
    jPanel2.add(btnUm, new org.netbeans.lib.awtextra.AbsoluteConstraints(20, 260, -1, -1));

    btnDois.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnDois.setForeground(new java.awt.Color(55, 62, 71));
    btnDois.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnDois.setText("2");
    btnDois.setFocusPainted(false);
    btnDois.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnDois.setMaximumSize(new java.awt.Dimension(20, 20));
    btnDois.setMinimumSize(new java.awt.Dimension(20, 20));
    btnDois.setPreferredSize(new java.awt.Dimension(50, 50));
    btnDois.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnDois.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnDois.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnDoisActionPerformed(evt);
        }
    });
    jPanel2.add(btnDois, new org.netbeans.lib.awtextra.AbsoluteConstraints(100, 260, -1, -1));

    btnTres.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnTres.setForeground(new java.awt.Color(55, 62, 71));
    btnTres.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnTres.setText("3");
    btnTres.setFocusPainted(false);
    btnTres.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnTres.setMaximumSize(new java.awt.Dimension(20, 20));
    btnTres.setMinimumSize(new java.awt.Dimension(20, 20));
    btnTres.setPreferredSize(new java.awt.Dimension(50, 50));
    btnTres.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnTres.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnTres.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnTresActionPerformed(evt);
        }
    });
    jPanel2.add(btnTres, new org.netbeans.lib.awtextra.AbsoluteConstraints(180, 260, -1, -1));

    btnZero.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnZero.setForeground(new java.awt.Color(55, 62, 71));
    btnZero.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnZero.setText("0");
    btnZero.setFocusPainted(false);
    btnZero.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnZero.setMaximumSize(new java.awt.Dimension(20, 20));
    btnZero.setMinimumSize(new java.awt.Dimension(20, 20));
    btnZero.setPreferredSize(new java.awt.Dimension(50, 50));
    btnZero.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnZero.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnZero.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnZeroActionPerformed(evt);
        }
    });
    jPanel2.add(btnZero, new org.netbeans.lib.awtextra.AbsoluteConstraints(20, 340, -1, -1));

    btnPonto.setFont(new java.awt.Font("Roboto Light", 0, 24)); // NOI18N
    btnPonto.setForeground(new java.awt.Color(55, 62, 71));
    btnPonto.setIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    btnPonto.setText(".");
    btnPonto.setFocusPainted(false);
    btnPonto.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    btnPonto.setMaximumSize(new java.awt.Dimension(20, 20));
    btnPonto.setMinimumSize(new java.awt.Dimension(20, 20));
    btnPonto.setPreferredSize(new java.awt.Dimension(50, 50));
    btnPonto.setPressedIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    btnPonto.setRolloverIcon(new javax.swing.ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    btnPonto.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            btnPontoActionPerformed(evt);
        }
    });
    jPanel2.add(btnPonto, new org.netbeans.lib.awtextra.AbsoluteConstraints(100, 340, -1, -1));

    getContentPane().add(jPanel2, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 160, 330, 400));

    pack();
}// </editor-fold>                        

public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(Calculadora.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Calculadora().setVisible(true);
        }
    });
}

public void addNumero(String digito){
    txtOperacoes.setText(txtOperacoes.getText()+digito);
}

private void btnIgualActionPerformed(java.awt.event.ActionEvent evt) {

É aqui que tento fazer a operação
try{
String resultado = se.eval(txtOperacoes.getText()).toString();
txtResultado.setText(resultado);
} catch(Exception e){
txtOperacoes.setText(“ERRO”);
}
}

private void btnNoveActionPerformed(java.awt.event.ActionEvent evt) {                                        
    addNumero("9");
    btnIgual.doClick();
}                                                                                                                         

private void btnDivisaoActionPerformed(java.awt.event.ActionEvent evt) {                                           
    addNumero("/");
}                                          

private void btnMutiplicacaoActionPerformed(java.awt.event.ActionEvent evt) {                                                
    addNumero("*");
}                                               

private void btnMenosActionPerformed(java.awt.event.ActionEvent evt) {                                         
    addNumero("-");
}                                        

private void btnMaisActionPerformed(java.awt.event.ActionEvent evt) {                                        
    addNumero("+");
}                                       

private void btnApagarActionPerformed(java.awt.event.ActionEvent evt) {                                          
    txtOperacoes.setText("");
    txtResultado.setText("");
}                                         

private void btnSeteActionPerformed(java.awt.event.ActionEvent evt) {                                        
    addNumero("7");
    btnIgual.doClick();
}                                       

private void btnOitoActionPerformed(java.awt.event.ActionEvent evt) {                                        
     addNumero("8");
     btnIgual.doClick();
}                                       

private void btnQuatroActionPerformed(java.awt.event.ActionEvent evt) {                                          
     addNumero("4");
     btnIgual.doClick();
}                                         

private void btnCincoActionPerformed(java.awt.event.ActionEvent evt) {                                         
     addNumero("5");
     btnIgual.doClick();
}                                        

private void btnSeisActionPerformed(java.awt.event.ActionEvent evt) {                                        
     addNumero("6");
     btnIgual.doClick();
}                                       

private void btnUmActionPerformed(java.awt.event.ActionEvent evt) {                                      
     addNumero("1");
     btnIgual.doClick();
}                                     

private void btnDoisActionPerformed(java.awt.event.ActionEvent evt) {                                        
     addNumero("2");
     btnIgual.doClick();
}                                       

private void btnTresActionPerformed(java.awt.event.ActionEvent evt) {                                        
     addNumero("3");
     btnIgual.doClick();
}                                       

private void btnZeroActionPerformed(java.awt.event.ActionEvent evt) {                                        
     addNumero("0");
     btnIgual.doClick();
}                                                                        


// Variables declaration - do not modify                     
private javax.swing.JButton btnApagar;
private javax.swing.JButton btnCinco;
private javax.swing.JButton btnDivisao;
private javax.swing.JButton btnDois;
private javax.swing.JButton btnIgual;
private javax.swing.JButton btnMais;
private javax.swing.JButton btnMenos;
private javax.swing.JButton btnMutiplicacao;
private javax.swing.JButton btnNove;
private javax.swing.JButton btnOito;
private javax.swing.JButton btnPonto;
private javax.swing.JButton btnPorcentagem;
private javax.swing.JButton btnPotencia;
private javax.swing.JButton btnQuatro;
private javax.swing.JButton btnSeis;
private javax.swing.JButton btnSete;
private javax.swing.JButton btnTres;
private javax.swing.JButton btnUm;
private javax.swing.JButton btnZero;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JLabel txtOperacoes;
private javax.swing.JLabel txtResultado;
// End of variables declaration                   

}

Imagem

Coloque para printar o stack trace:

  try {
    String resultado = se.eval(txtOperacoes.getText()).toString();
    txtResultado.setText(resultado);
  } catch(Exception e){
    e.printStackTrace(); //PRINTANDO PARA SABER A CAUSA
    txtOperacoes.setText(“ERRO”);
  }

Deu uma lista de erros gigantes

java.lang.NullPointerException: Cannot invoke “javax.script.ScriptEngine.eval(String)” because “this.se” is null

Deu isso ai

Por qual motivo você está usando um ScriptEngine para implementar a calculadora?

Parece que é para usar o método eval do javascript.

Tente assim:
new ScriptEngineManager(null);

Eu tentei e continua dando o mesmo erro

Eu vi que usando ele eu poderia usar um método do java script que já me realizaria as contas, vc sabe algum outro que posso usar ?

Dicas: faça um favor a si mesmo e use os import's a seu favor.

Em vez de usar o nome completo da classe:

jPanel1 = new javax.swing.JPanel();

Coloque um import no início e use somente o nome da classe no restante do código:

// antes da classe
import javax.swing.JPanel;

// e dentro da classe
jPanel1 = new Panel();

Faça isso para todas as classes que você usa, que o código fica não só mais curto, como também mais legível.

E coloque código repetitivo em métodos, que facilita muito sua vida. Por exemplo, repare que os botões possuem muitos atributos em comum, mudando apenas o label e o que acontece quando ele é clicado. Então poderia ser algo como:

// método que gera um botão com número
private JButton criarBotaoNumero(String numero) {
    JButton button = new JButton();
    button.setFont(new Font("Roboto Light", 0, 24)); // NOI18N
    button.setForeground(new Color(55, 62, 71));
    button.setIcon(new ImageIcon(getClass().getResource("/com/mycompany/imagens/btn2.png"))); // NOI18N
    button.setText(numero);
    button.setFocusPainted(false);
    button.setHorizontalTextPosition(SwingConstants.CENTER);
    button.setMaximumSize(new Dimension(20, 20));
    button.setMinimumSize(new Dimension(20, 20));
    button.setPreferredSize(new Dimension(50, 50));
    button.setPressedIcon(new ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1.png"))); // NOI18N
    button.setRolloverIcon(new ImageIcon(getClass().getResource("/com/mycompany/imagens/btn1_press.png"))); // NOI18N
    button.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent evt) {
            addNumero(numero);
            btnIgual.doClick();
        }
    });
    return button;
}

E aí no construtor, você cria os botões usando o método acima:

jPanel2.add(criarBotaoNumero("0"), new AbsoluteConstraints(20, 340, -1, -1));
jPanel2.add(criarBotaoNumero("3"), new AbsoluteConstraints(180, 260, -1, -1));
// etc...

E repare que nesse caso nem precisaria criar as variáveis btnTres, btnZero, etc, e nem os respectivos métodos actionPerformed. Em vez disso, eu chamo o addNumero passando o número correspondente ao botão e o click no botão de igual.

Dá para fazer coisas similares com os botões das operações.