feat: only download java if not present

src/instance/instance.ts

@@ -14,6 +14,7 @@ import { installForge } from "../core/modloaders";
 import { getJavaExecutable } from "../core/java";
 import { readJson } from "../utils/fs";
 import { mergeManifests } from "../core/mergeManifests";
+import { exec } from "node:child_process";
 
 function getJavaOs() {
   switch (os()) {
@@ -58,6 +59,20 @@ interface InstanceEvents {
   ];
 }
 
+function checkJava(javaLocation: string) {
+  const javaExe = getJavaExecutable(javaLocation);
+
+  return new Promise<boolean>((res) => {
+    exec(`${javaExe} -version`, (err) => {
+      if (err) {
+        res(false);
+      } else {
+        res(true);
+      }
+    });
+  });
+}
+
 export class Instance extends EventEmitter<InstanceEvents> {
   version: string;
   modloader?: Modloader;
@@ -117,7 +132,7 @@ export class Instance extends EventEmitter<InstanceEvents> {
     this.args.game = game || "";
   }
 
-  async initialize() {
+  private async initialize() {
     this.versionLocation = path.join(this.paths.versions, this.version);
     this.instanceLocation = path.join(this.paths.instances, this.version);
 
@@ -209,6 +224,7 @@ export class Instance extends EventEmitter<InstanceEvents> {
       error.throw();
     }
 
+    if (!await checkJava(this.javaLocation)) {
       try {
         const javaDownloader = await core.java.JavaDownloader(
           getJavaOs(),
@@ -230,6 +246,7 @@ export class Instance extends EventEmitter<InstanceEvents> {
         const error = new InstallError("java", original);
         error.throw();
       }
+    }
 
     if (this.modloader) {
       try {