diff --git a/craco.config.js b/craco.config.js
index 6c8c6a5d34..9ced7dac49 100644
--- a/craco.config.js
+++ b/craco.config.js
@@ -18,7 +18,7 @@ const cracoConfig = {
         plugin => plugin.constructor.name === 'InjectManifest'
       );
       if (injectManifestPlugin) {
-        injectManifestPlugin.config.maximumFileSizeToCacheInBytes = 17 * 1024 * 1024;
+        injectManifestPlugin.config.maximumFileSizeToCacheInBytes = 20 * 1024 * 1024;
       }
 
       // add rules to pack WASM (for Sourceror)
@@ -47,9 +47,10 @@ const cracoConfig = {
         'https': require.resolve('https-browserify'),
         'os': require.resolve('os-browserify/browser'),
         'path/posix': require.resolve('path-browserify'),
+        'process/browser': require.resolve('process/browser'),
         'stream': require.resolve('stream-browserify'),
         'timers': require.resolve('timers-browserify'),
-        'url': require.resolve('url/')
+        'url': require.resolve('url/'),
       };
 
       // workaround .mjs files by Acorn
@@ -138,6 +139,7 @@ const cracoConfig = {
           'split-on-first',
           'filter-obj',
           '@sourceacademy/c-slang',
+          'java-parser'
         ),
         '^.+\\.module\\.(css|sass|scss)$'
       ];
diff --git a/package.json b/package.json
index 5d28df86bc..ef9f067938 100644
--- a/package.json
+++ b/package.json
@@ -51,8 +51,8 @@
     "flexboxgrid": "^6.3.1",
     "flexboxgrid-helpers": "^1.1.3",
     "hastscript": "^9.0.0",
-    "java-slang": "^1.0.6",
     "js-slang": "^1.0.66",
+    "java-slang": "^1.0.13",
     "js-yaml": "^4.1.0",
     "konva": "^9.2.0",
     "lodash": "^4.17.21",
diff --git a/src/commons/utils/JavaHelper.ts b/src/commons/utils/JavaHelper.ts
index 21ddc66f51..42eea82175 100644
--- a/src/commons/utils/JavaHelper.ts
+++ b/src/commons/utils/JavaHelper.ts
@@ -1,3 +1,5 @@
+import { compileFromSource, typeCheck } from 'java-slang';
+import { BinaryWriter } from 'java-slang/dist/compiler/binary-writer';
 import setupJVM, { parseBin } from 'java-slang/dist/jvm';
 import { createModuleProxy, loadCachedFiles } from 'java-slang/dist/jvm/utils/integration';
 import { Context } from 'js-slang';
@@ -9,6 +11,33 @@ import DisplayBufferService from './DisplayBufferService';
 export async function javaRun(javaCode: string, context: Context) {
   let compiled = {};
 
+  const stderr = (type: 'TypeCheck' | 'Compile' | 'Runtime', msg: string) => {
+    context.errors.push({
+      type: type as any,
+      severity: 'Error' as any,
+      location: { start: { line: -1, column: -1 }, end: { line: -1, column: -1 } },
+      explain: () => msg,
+      elaborate: () => msg
+    });
+  };
+
+  const typeCheckResult = typeCheck(javaCode);
+  if (typeCheckResult.hasTypeErrors) {
+    const typeErrMsg = typeCheckResult.errorMsgs.join('\n');
+    stderr('TypeCheck', typeErrMsg);
+    return Promise.resolve({ status: 'error' });
+  }
+
+  try {
+    const classFile = compileFromSource(javaCode);
+    compiled = {
+      'Main.class': Buffer.from(new BinaryWriter().generateBinary(classFile)).toString('base64')
+    };
+  } catch (e) {
+    stderr('Compile', e);
+    return Promise.resolve({ status: 'error' });
+  }
+
   let files = {};
   let buffer: string[] = [];
 
@@ -46,6 +75,7 @@ export async function javaRun(javaCode: string, context: Context) {
     }
     return parseBin(new DataView(bytes.buffer));
   };
+
   const loadNatives = async (path: string) => {
     // dynamic load modules
     if (path.startsWith('modules')) {
@@ -56,6 +86,7 @@ export async function javaRun(javaCode: string, context: Context) {
     }
     return await import(`java-slang/dist/jvm/stdlib/${path}.js`);
   };
+
   const stdout = (str: string) => {
     if (str.endsWith('\n')) {
       buffer.push(str);
@@ -67,33 +98,6 @@ export async function javaRun(javaCode: string, context: Context) {
       buffer.push(str);
     }
   };
-  const stderr = (msg: string) => {
-    context.errors.push({
-      type: 'Runtime' as any,
-      severity: 'Error' as any,
-      location: {
-        start: {
-          line: -1,
-          column: -1
-        },
-        end: {
-          line: -1,
-          column: -1
-        }
-      },
-      explain: () => msg,
-      elaborate: () => msg
-    });
-  };
-
-  // FIXME: Remove when the compiler is working
-  try {
-    const json = JSON.parse(javaCode);
-    compiled = json;
-  } catch (e) {
-    stderr(e);
-    return Promise.resolve({ status: 'error' });
-  }
 
   // load cached classfiles from IndexedDB
   return loadCachedFiles(() =>
@@ -119,12 +123,20 @@ export async function javaRun(javaCode: string, context: Context) {
             readFileSync: readClassFiles,
             readFile: loadNatives,
             stdout,
-            stderr,
+            stderr: (msg: string) => stderr('Runtime', msg),
             onFinish: () => {
               resolve(
                 context.errors.length
                   ? { status: 'error' }
-                  : { status: 'finished', context, value: '' }
+                  : {
+                      status: 'finished',
+                      context,
+                      value: new (class {
+                        toString() {
+                          return ' ';
+                        }
+                      })()
+                    }
               );
             }
           },
diff --git a/src/setupTests.ts b/src/setupTests.ts
index 325a68de3a..342d11a07b 100644
--- a/src/setupTests.ts
+++ b/src/setupTests.ts
@@ -8,3 +8,10 @@ jest.mock('./commons/utils/notifications/createNotification', () => ({
     show: jest.fn()
   }
 }));
+
+jest.mock('java-slang', () => {
+  return {
+    compileFromSource: () => '',
+    typeCheck: () => ({ hasTypeErrors: false, errorMsgs: [] })
+  };
+});
diff --git a/yarn.lock b/yarn.lock
index caff454791..021ca1a104 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -8024,10 +8024,10 @@ java-parser@^2.0.5:
     chevrotain-allstar "0.3.1"
     lodash "4.17.21"
 
-java-slang@^1.0.6:
-  version "1.0.6"
-  resolved "https://registry.yarnpkg.com/java-slang/-/java-slang-1.0.6.tgz#34a68954a8dfb5bde8572d49a6bea170d7026749"
-  integrity sha512-CHq2s9xuzuuPfygRp9pQncfPfIuzpHivXn3wfy4QBiQ801IvdVFL3w/nV6qQn6GUG+kvOU+qCuxUFsFH8X5Dhg==
+java-slang@^1.0.13:
+  version "1.0.13"
+  resolved "https://registry.yarnpkg.com/java-slang/-/java-slang-1.0.13.tgz#601454c9dd28a41ea6918dab51a7e65401d2c2d9"
+  integrity sha512-xBh84Gcp7iyc3o9bWDbaIa7GXf75tpUVmDrd/gXIAU/gxNARitJdl5xCjQW5y4iesqwucV7cY+Ewx6MIt4xKeQ==
   dependencies:
     "@types/lodash" "^4.14.198"
     java-parser "^2.0.5"