{"id":243,"date":"2017-12-04T02:41:00","date_gmt":"2017-12-04T02:41:00","guid":{"rendered":"https:\/\/kindsonthegenius.com\/blog\/2017\/12\/04\/how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/"},"modified":"2026-07-05T01:48:08","modified_gmt":"2026-07-04T23:48:08","slug":"how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots","status":"publish","type":"post","link":"https:\/\/kindsonthegenius.com\/blog\/how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/","title":{"rendered":"How to Build a Simple Calculator in Java Using NetBeans \u2014 Step by Step (2026)"},"content":{"rendered":"<p><!-- ktg-updated-banner --><\/p>\n<div class=\"ktg-updated-banner\" style=\"margin:1em 0;padding:0.75em 1em;background:#eff6ff;border-left:4px solid #3b82f6;border-radius:4px;\">\n<p><strong>Updated July 5, 2026:<\/strong> Restructured for clarity, added table of contents, FAQ answers, and links to <a href=\"https:\/\/kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/\">Part 2<\/a>. Screenshots and code reviewed for NetBeans 21+.<\/p>\n<\/div>\n<p>Learn how to <strong>build a simple calculator in Java using NetBeans<\/strong> \u2014 a classic beginner project that teaches GUI design, Swing components, and event-driven programming. In this <strong>Part 1<\/strong> tutorial you will design the calculator layout, wire number and operator buttons, and implement basic arithmetic for digits 0\u20139.<\/p>\n<p><strong>Prerequisites:<\/strong> If you are new to Java and NetBeans, complete these lessons first:<\/p>\n<ul>\n<li><a href=\"https:\/\/kindsonthegenius.com\/blog\/java-progamming-for-beginners-lesson-1-introduction-to-java-and-intallation-of-netbeans\/\">Lesson 1 \u2014 Introduction to Java &amp; NetBeans Installation<\/a><\/li>\n<li><a href=\"https:\/\/kindsonthegenius.com\/blog\/java-progamming-for-beginners-lesson-2-write-your-first-java-program\/\">Lesson 2 \u2014 Write Your First Java Program<\/a><\/li>\n<\/ul>\n<p><strong>Estimated time:<\/strong> 60\u201390 minutes. <strong>Difficulty:<\/strong> Beginner.<\/p>\n<p><!-- ktg-article-toc --><\/p>\n<nav class=\"ktg-article-toc\" aria-label=\"Java calculator tutorial table of contents\" style=\"margin:1.5em 0;padding:1em 1.25em;background:#f8fafc;border:1px solid #e2e8f0;border-radius:8px;\">\n<h2>Table of Contents<\/h2>\n<ol>\n<li><a href=\"#what-you-build\">What you will build<\/a><\/li>\n<li><a href=\"#requirements\">What you need<\/a><\/li>\n<li><a href=\"#create-project\">Create the NetBeans project<\/a><\/li>\n<li><a href=\"#design-gui\">Design the calculator GUI<\/a><\/li>\n<li><a href=\"#preview-form\">Preview the form<\/a><\/li>\n<li><a href=\"#add-variables\">Add calculator state variables<\/a><\/li>\n<li><a href=\"#number-buttons\">Wire number buttons (0\u20139)<\/a><\/li>\n<li><a href=\"#clear-operators\">Clear and operator buttons<\/a><\/li>\n<li><a href=\"#equals-button\">Equals button and calculation<\/a><\/li>\n<li><a href=\"#test-calculator\">Test your calculator<\/a><\/li>\n<li><a href=\"#faq\">Frequently asked questions<\/a><\/li>\n<li><a href=\"#next-steps\">Continue to Part 2<\/a><\/li>\n<\/ol>\n<\/nav>\n<h2 id=\"what-you-build\">What You Will Build<\/h2>\n<p>A desktop calculator application with:<\/p>\n<ul>\n<li>A <code>JTextField<\/code> display (<code>txtResult<\/code>)<\/li>\n<li>Number buttons 0\u20139 and operator buttons (+, \u2212, \u00d7, \u00f7)<\/li>\n<li>Clear (CE) and equals (=) buttons<\/li>\n<li>Mouse-click event handlers that perform addition, subtraction, multiplication, and division<\/li>\n<\/ul>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/4.bp.blogspot.com\/-zuRztnFRnBk\/WiS1mgly_3I\/AAAAAAAAAVM\/sas2_5hwZE4klSoHc6HQ1RJxv4uT4v7SACLcBGAs\/s640\/Build-a-Simple-Calculator-In-Java-Using-Netbeans.jpg\" alt=\"Simple calculator GUI built in Java NetBeans with number pad and operators\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><figcaption style=\"font-size:0.85em;color:#666;margin-top:0.5em;\">Finished calculator layout in NetBeans Design view<\/figcaption><\/figure>\n<h2 id=\"requirements\">What You Need<\/h2>\n<ul>\n<li><strong>NetBeans IDE<\/strong> (with Java SE support) \u2014 see <a href=\"https:\/\/kindsonthegenius.com\/blog\/java-progamming-for-beginners-lesson-1-introduction-to-java-and-intallation-of-netbeans\/\">Lesson 1<\/a> for installation<\/li>\n<li>A computer running Windows, macOS, or Linux<\/li>\n<li>Optional: pen and paper to sketch the layout before building<\/li>\n<\/ul>\n<h2 id=\"create-project\">Step 1\u20132: Create the NetBeans Project and JFrame Form<\/h2>\n<h3>Step 1: Create an application<\/h3>\n<p>In NetBeans, choose <strong>File \u2192 New Project \u2192 Java with Ant \u2192 Java Application<\/strong>. Name the project <code>CalculatorProgram<\/code>. If you need help creating a project, follow <a href=\"https:\/\/kindsonthegenius.com\/blog\/java-progamming-for-beginners-lesson-2-write-your-first-java-program\/\">Your First Java Program<\/a>.<\/p>\n<h3>Step 2: Add a JFrame Form<\/h3>\n<p>Right-click the project in the <strong>Projects<\/strong> tab \u2192 <strong>New \u2192 JFrame Form<\/strong>. Set the class name to <code>pnlCalculator<\/code> and click <strong>Finish<\/strong>.<\/p>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/3.bp.blogspot.com\/-bu3pJ5HRQKg\/WiSeVAg7A6I\/AAAAAAAAAUI\/HTrsXYgKFCkryLoGMS20_JP0G_1KbD6FwCLcBGAs\/s640\/Adding%2Ba%2BJFrame%2BForm.JPG\" alt=\"Adding a JFrame Form named pnlCalculator in NetBeans New File wizard\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h2 id=\"design-gui\">Step 3\u20137: Design the Calculator GUI<\/h2>\n<h3>Step 3: Add JPanels<\/h3>\n<p>From the <strong>Palette<\/strong>, drag two <strong>JPanel<\/strong> components onto the form. Resize and position them \u2014 one panel for the display area, one for the button grid.<\/p>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/3.bp.blogspot.com\/-b0duSz4QG2w\/WiSeU5dDXYI\/AAAAAAAAAUE\/akZmY524biQOhxIhzvZJQG7hDeeBLc_0wCEwYBhgL\/s640\/Adding%2Btwo%2BJPanels.JPG\" alt=\"Two JPanels positioned on the NetBeans calculator form\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h3>Step 4: Add and rename the display TextField<\/h3>\n<p><strong>Step 4a:<\/strong> Place a <strong>JTextField<\/strong> in the upper panel.<\/p>\n<p><strong>Step 4b:<\/strong> Right-click the field \u2192 <strong>Edit Text<\/strong> \u2192 delete the default text. Right-click again \u2192 <strong>Change Variable Name<\/strong> \u2192 enter <code>txtResult<\/code>.<\/p>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/3.bp.blogspot.com\/-72geiVb5VNM\/WiSeUmImUyI\/AAAAAAAAAUA\/rrqZ12y8AaYFPmOxunP6xrl1IZqseKz6wCEwYBhgL\/s640\/Adding%2Ba%2BTextField.JPG\" alt=\"JTextField txtResult placed on the calculator form display area\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h3>Step 5\u20136: Add and label buttons<\/h3>\n<p>From the Palette, add <strong>JButton<\/strong> components for digits 0\u20139, operators (+, \u2212, \u00d7, \u00f7), CE (clear), +\/-, and = (equals). Resize until the grid matches a standard calculator.<\/p>\n<p>Right-click each button \u2192 <strong>Edit Text<\/strong> and set the visible labels: <code>1<\/code>, <code>2<\/code>, \u2026 <code>9<\/code>, <code>0<\/code>, <code>+<\/code>, <code>-<\/code>, <code>*<\/code>, <code>\/<\/code>, <code>CE<\/code>, <code>+\/-<\/code>, <code>=<\/code>.<\/p>\n<h3>Step 7: Rename button variables<\/h3>\n<p>Right-click each button \u2192 <strong>Change Variable Name<\/strong>. Use these names exactly \u2014 typos cause compile errors:<\/p>\n<table>\n<thead>\n<tr>\n<th>Button label<\/th>\n<th>Variable name<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1\u20139, 0<\/td>\n<td><code>btn1<\/code> \u2026 <code>btn9<\/code>, <code>btn0<\/code><\/td>\n<\/tr>\n<tr>\n<td>+\/-<\/td>\n<td><code>btnPlusMinus<\/code> (optional in Part 1 \u2014 see <a href=\"#faq\">FAQ<\/a>)<\/td>\n<\/tr>\n<tr>\n<td>CE<\/td>\n<td><code>btnClear<\/code><\/td>\n<\/tr>\n<tr>\n<td>+<\/td>\n<td><code>btnPlus<\/code><\/td>\n<\/tr>\n<tr>\n<td>\u2212<\/td>\n<td><code>btnMinus<\/code><\/td>\n<\/tr>\n<tr>\n<td>\/<\/td>\n<td><code>btnDivision<\/code><\/td>\n<\/tr>\n<tr>\n<td>*<\/td>\n<td><code>btnMultiplication<\/code><\/td>\n<\/tr>\n<tr>\n<td>=<\/td>\n<td><code>btnEquals<\/code> (if your form auto-names it <code>jButton*<\/code>, rename it)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/4.bp.blogspot.com\/-VXX7Ov9wT2s\/WiSeWn5Q1YI\/AAAAAAAAAUs\/BtKbfQLSd7A7AdxTYW-MZxwOt0B74JldACEwYBhgL\/s640\/Completed%2BForm%2BDesign.JPG\" alt=\"Completed NetBeans calculator form with all buttons labeled and positioned\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h2 id=\"preview-form\">Step 8: Preview the Form<\/h2>\n<p>In the Projects tab, right-click <code>pnlCalculator.java<\/code> \u2192 <strong>Run File<\/strong>. The calculator window should appear with your layout. Close it when done.<\/p>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/3.bp.blogspot.com\/-uzZdN3DAwOA\/WiStZD4RwnI\/AAAAAAAAAU4\/3duTxV7O0E4mVTBJ3b6aZjJtMBTYGELjACLcBGAs\/s640\/RunFile.jpg\" alt=\"Running pnlCalculator.java from NetBeans Projects tab\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><figcaption style=\"font-size:0.85em;color:#666;margin-top:0.5em;\">Right-click the form file and choose Run File to preview<\/figcaption><\/figure>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/2.bp.blogspot.com\/-pbmhjEWb_UA\/WiSeYRzHTTI\/AAAAAAAAAUs\/eyEfnwyPsYsfjqB7j126rUZKgp3vMM6zQCEwYBhgL\/s640\/Finished-Form-Run.JPG\" alt=\"Calculator form preview window showing button layout before adding code\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h2 id=\"add-variables\">Step 9\u201310: Add Calculator State Variables<\/h2>\n<p>Switch to the <strong>Source<\/strong> view of <code>pnlCalculator.java<\/code>. Scroll to the class body (below the generated fields, before the constructor) and add:<\/p>\n<pre><code class=\"language-java\">static int value1;\nstatic int value2;\nstatic String operator;\n<\/code><\/pre>\n<p>These <code>static<\/code> fields store the first operand, second operand, and selected operation. They must be declared at <strong>class level<\/strong> (not inside a method) so every button handler can access them.<\/p>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/-Edu9meRB1os\/WiSeZcyWyPI\/AAAAAAAAAUs\/43V1AN3UvcwoSAwFuIwbJ54oMxipYlVowCEwYBhgL\/s640\/Where%2Bto%2BWrite%2Bthe%2Bfirst%2Bcode.JPG\" alt=\"Location in NetBeans source view to add static calculator variables\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h2 id=\"number-buttons\">Step 11\u201316: Wire Number Buttons (0\u20139)<\/h2>\n<h3>Step 11\u201312: Button 1 handler<\/h3>\n<p>Right-click <strong>button 1<\/strong> in Design view \u2192 <strong>Events \u2192 Mouse \u2192 mouseClicked<\/strong>. NetBeans generates <code>btn1MouseClicked<\/code>. Inside that method (below the <code>\/\/ TODO<\/code> comment), add:<\/p>\n<pre><code class=\"language-java\">if (txtResult.getText().isEmpty()) {\n    txtResult.setText(btn1.getText());\n    value1 = 1;\n} else {\n    txtResult.setText(txtResult.getText() + \" \" + btn1.getText());\n    value2 = 1;\n}\n<\/code><\/pre>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/4.bp.blogspot.com\/-aXCnfQp3p2Y\/WiSeYwKy6SI\/AAAAAAAAAUs\/LYyi7pVK3okfETdRdV1xh9SfuAt9hUYAACEwYBhgL\/s640\/Go%2Bto%2BButton1%2BAction.jpg\" alt=\"Creating mouseClicked event handler for button 1 in NetBeans\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/4.bp.blogspot.com\/-CbWZuBRvCbg\/WiSeadm30KI\/AAAAAAAAAUs\/fcIuiawhA9QgeQ-3tjWs-vYdmL5I1UBEwCEwYBhgL\/s640\/Where-to-write-button-1-code.JPG\" alt=\"btn1MouseClicked method location in NetBeans source editor\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/2.bp.blogspot.com\/-VBxmnzjeK5M\/WiSeaPUJb0I\/AAAAAAAAAUs\/3IZBzX150IkE3jLsEJh3w4PFcW6qlztEgCEwYBhgL\/s640\/Where-to-write-button-1-code-written.JPG\" alt=\"Button 1 click handler code written in NetBeans Java source\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<h3>Step 13: Test button 1<\/h3>\n<p>Run the form again. Click <strong>1<\/strong> \u2014 the digit should appear in <code>txtResult<\/code>.<\/p>\n<h3>Step 14\u201316: Repeat for buttons 2\u20130<\/h3>\n<p>For each remaining digit button, create a <code>mouseClicked<\/code> handler and use the same pattern, changing the button reference and integer value. Example for button 2:<\/p>\n<pre><code class=\"language-java\">if (txtResult.getText().isEmpty()) {\n    txtResult.setText(btn2.getText());\n    value1 = 2;\n} else {\n    txtResult.setText(txtResult.getText() + \" \" + btn2.getText());\n    value2 = 2;\n}\n<\/code><\/pre>\n<figure style=\"margin:1.5em 0;text-align:center;\"><img decoding=\"async\" src=\"https:\/\/1.bp.blogspot.com\/--145Uf8TVXQ\/WiSeWeOVIuI\/AAAAAAAAAUs\/5C1Sk_GGr28ul-pGgzGn0wA7ghLeonn_gCEwYBhgL\/s640\/Button1-and-2-Code-Written.JPG\" alt=\"NetBeans source showing click handlers for calculator buttons 1 and 2\" width=\"640\" height=\"480\" loading=\"lazy\" style=\"max-width:100%;height:auto;border-radius:8px;border:1px solid #dee2e6;\" \/><\/figure>\n<p><strong>Steps 17\u201318:<\/strong> Review your handlers for typos, then run the program and test all digit buttons.<\/p>\n<h2 id=\"clear-operators\">Step 19\u201320: Clear and Operator Buttons<\/h2>\n<h3>Step 19: Clear (CE) button<\/h3>\n<p>Add a <code>mouseClicked<\/code> handler for <code>btnClear<\/code>:<\/p>\n<pre><code class=\"language-java\">txtResult.setText(\"\");\n<\/code><\/pre>\n<h3>Step 20: Plus, minus, division, and multiplication<\/h3>\n<p>For each operator button, set the <code>operator<\/code> string and append the symbol to the display:<\/p>\n<pre><code class=\"language-java\">\/\/ btnPlus\nif (!txtResult.getText().isEmpty()) {\n    operator = \"plus\";\n    txtResult.setText(txtResult.getText() + \" +\");\n}\n\n\/\/ btnMinus\nif (!txtResult.getText().isEmpty()) {\n    operator = \"minus\";\n    txtResult.setText(txtResult.getText() + \" -\");\n}\n\n\/\/ btnDivision\nif (!txtResult.getText().isEmpty()) {\n    operator = \"division\";\n    txtResult.setText(txtResult.getText() + \" \/\");\n}\n\n\/\/ btnMultiplication\nif (!txtResult.getText().isEmpty()) {\n    operator = \"multiplication\";\n    txtResult.setText(txtResult.getText() + \" *\");\n}\n<\/code><\/pre>\n<h2 id=\"equals-button\">Step 21\u201322: Equals Button and Calculation<\/h2>\n<p>After testing operators, clicking <strong>=<\/strong> does nothing until you add the equals handler. Create <code>btnEqualsMouseClicked<\/code> (or the auto-generated name for your = button) with:<\/p>\n<pre><code class=\"language-java\">double answer = 0;\nif (\"plus\".equals(operator))\n    answer = value1 + value2;\nelse if (\"minus\".equals(operator))\n    answer = value1 - value2;\nelse if (\"multiplication\".equals(operator))\n    answer = value1 * value2;\nelse if (\"division\".equals(operator))\n    answer = value1 \/ value2;\n\nString result = Double.toString(answer);\ntxtResult.setText(result);\n<\/code><\/pre>\n<p><strong>Important:<\/strong> Compare strings with <code>\"plus\".equals(operator)<\/code>, not <code>operator == \"plus\"<\/code>. In Java, <code>==<\/code> compares object references; <code>.equals()<\/code> compares content. Using <code>==<\/code> on strings is a common cause of wrong or missing results.<\/p>\n<h2 id=\"test-calculator\">Step 23: Test Your Calculator<\/h2>\n<p>Run the program and try <code>4 + 5 =<\/code>. You should see <code>9.0<\/code> in the display. Test subtraction, multiplication, division, and CE.<\/p>\n<p><strong>Limitation in Part 1:<\/strong> This version works with single digits 0\u20139 only. <a href=\"https:\/\/kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/\">Part 2<\/a> covers multi-digit input, the +\/- toggle, and error handling.<\/p>\n<h2 id=\"faq\">Frequently Asked Questions<\/h2>\n<p><strong>What is the code for the +\/- (plus-minus) button?<\/strong><br \/>\nThe +\/- button (<code>btnPlusMinus<\/code>) is not implemented in Part 1. It is covered in <a href=\"https:\/\/kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/\">Part 2<\/a>, which adds sign toggling and multi-digit support.<\/p>\n<p><strong>I get an error on <code>getText()<\/code> \u2014 how do I fix it?<\/strong><br \/>\nEnsure the display field is renamed to <code>txtResult<\/code> (Step 4b) and that you are calling <code>txtResult.getText()<\/code> inside the <code>pnlCalculator<\/code> class. If NetBeans shows <code>cannot find symbol<\/code>, the variable name in Design view does not match your code.<\/p>\n<p><strong>My <code>operator<\/code> variable is not recognized in the equals button code.<\/strong><br \/>\nDeclare <code>static String operator;<\/code> at <strong>class level<\/strong> (Step 10), not inside a single button method. All handlers must share the same field.<\/p>\n<p><strong>The calculator shows the wrong answer.<\/strong><br \/>\nUse <code>\"plus\".equals(operator)<\/code> instead of <code>operator == \"plus\"<\/code>. Also confirm you clicked an operator <em>before<\/em> the second digit so <code>value1<\/code> and <code>value2<\/code> are set correctly.<\/p>\n<p><strong>NetBeans says <code>jButton6<\/code> or <code>jButton9<\/code> is not recognized.<\/strong><br \/>\nRename every button in Design view (Step 7). Default names like <code>jButton1<\/code> must be changed to <code>btn1<\/code>, <code>btn2<\/code>, etc., or your handler code will not compile.<\/p>\n<p><strong>Where is Part 2?<\/strong><br \/>\n<a href=\"https:\/\/kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/\">Part 2: How to Build a Simple Calculator in Java Using NetBeans<\/a> \u2014 multi-digit numbers, +\/- toggle, and input validation.<\/p>\n<h2 id=\"next-steps\">Next Steps<\/h2>\n<ul>\n<li><a href=\"https:\/\/kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/\"><strong>Part 2<\/strong> \u2014 Multi-digit calculator, +\/- button, and error handling<\/a><\/li>\n<li><a href=\"https:\/\/kindsonthegenius.com\/blog\/java-for-beginners-lesson-3-structure-of-a-java-program\/\">Lesson 3 \u2014 Structure of a Java Program<\/a><\/li>\n<li><a href=\"https:\/\/kindsonthegenius.com\/blog\/15-easy-free-java-tutorials-with-step-by-step-examples-and-quiz\/\">15 Easy Free Java Tutorials<\/a><\/li>\n<li><a href=\"https:\/\/www.alkademy.com\/courses\" target=\"_blank\" rel=\"noopener noreferrer\">Alkademy Java courses<\/a> \u2014 live instructor-led classes<\/li>\n<\/ul>\n<p><!-- ktg-series-nav --><\/p>\n<nav class=\"ktg-series-nav\" aria-label=\"Java calculator tutorial series\">\n<p><strong>Next:<\/strong> <a href=\"https:\/\/kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/\">Part 2 \u2014 Multi-digit Calculator, +\/- Button &amp; Error Handling<\/a><\/p>\n<\/nav>\n<p><!-- ktg-alkademy-cta --><\/p>\n<div class=\"ktg-alkademy-cta\" style=\"margin:2em 0;padding:1.25em;border-left:4px solid #2563eb;background:#f8fafc;\">\n<p><strong>Want structured Java training?<\/strong> Join <a href=\"https:\/\/www.alkademy.com\/courses\" target=\"_blank\" rel=\"noopener noreferrer\">Alkademy<\/a> for instructor-led Java programming courses with hands-on projects.<\/p>\n<\/div>\n<p><!-- ktg-faq-schema --><br \/>\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"FAQPage\",\"mainEntity\":[{\"@type\":\"Question\",\"name\":\"What is the code for the +\/- button on the Java NetBeans calculator?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"The +\/- (plus-minus) button is not implemented in Part 1 of this tutorial. Part 2 covers sign toggling and multi-digit input.\"}},{\"@type\":\"Question\",\"name\":\"Why does getText() show an error in my NetBeans calculator project?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Rename the JTextField to txtResult in Design view and call txtResult.getText() inside the pnlCalculator class. A cannot find symbol error means the variable name in the form does not match your code.\"}},{\"@type\":\"Question\",\"name\":\"Why is my Java calculator giving the wrong answer?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Use equals() to compare operator strings, for example plus.equals(operator), not operator == plus. Also ensure value1 and value2 are set by clicking digits and an operator before pressing equals.\"}},{\"@type\":\"Question\",\"name\":\"Where is Part 2 of the Java calculator tutorial?\",\"acceptedAnswer\":{\"@type\":\"Answer\",\"text\":\"Part 2 is published at kindsonthegenius.com\/blog\/part-2-how-to-build-a-simple-calculator-in-java-using-netbeans-step-by-step-with-screenshots\/ and adds multi-digit numbers, the +\/- button, and error handling.\"}}]}<\/script><\/p>\n<p><!-- ktg-howto-schema --><br \/>\n<script type=\"application\/ld+json\">{\"@context\":\"https:\/\/schema.org\",\"@type\":\"HowTo\",\"name\":\"Build a Simple Calculator in Java Using NetBeans\",\"description\":\"Step-by-step guide to create a GUI calculator in Java with NetBeans Swing \u2014 JFrame form, buttons, and event handlers.\",\"totalTime\":\"PT90M\",\"tool\":[{\"@type\":\"HowToTool\",\"name\":\"NetBeans IDE\"}],\"step\":[{\"@type\":\"HowToStep\",\"name\":\"Create CalculatorProgram project\",\"text\":\"Create a new Java Application named CalculatorProgram in NetBeans.\"},{\"@type\":\"HowToStep\",\"name\":\"Add JFrame Form\",\"text\":\"Add a JFrame Form class named pnlCalculator to the project.\"},{\"@type\":\"HowToStep\",\"name\":\"Design the GUI\",\"text\":\"Add JPanels, a JTextField named txtResult, and JButton components for digits and operators.\"},{\"@type\":\"HowToStep\",\"name\":\"Add state variables\",\"text\":\"Declare static int value1, value2 and static String operator at class level.\"},{\"@type\":\"HowToStep\",\"name\":\"Wire button events\",\"text\":\"Create mouseClicked handlers for number, clear, operator, and equals buttons.\"},{\"@type\":\"HowToStep\",\"name\":\"Test the calculator\",\"text\":\"Run the form and verify arithmetic operations for digits 0 through 9.\"}]}<\/script><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Updated July 5, 2026: Restructured for clarity, added table of contents, FAQ answers, and links to Part 2. Screenshots and code reviewed for NetBeans 21+. &hellip; <\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"pagelayer_contact_templates":[],"_pagelayer_content":"","footnotes":""},"categories":[85],"tags":[],"class_list":["post-243","post","type-post","status-publish","format-standard","hentry","category-java"],"_links":{"self":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts\/243","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/comments?post=243"}],"version-history":[{"count":4,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts\/243\/revisions"}],"predecessor-version":[{"id":1849,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/posts\/243\/revisions\/1849"}],"wp:attachment":[{"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/media?parent=243"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/categories?post=243"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kindsonthegenius.com\/blog\/wp-json\/wp\/v2\/tags?post=243"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}