Add directory based locater, and some default directories.

Author: LexManos

src/main/java/net/minecraftforge/java_provisioner/Disco.java

@@ -607,6 +607,10 @@ private Arch(Arch parent, String key, String... names) {
             this.names = names;
         }
 
+        public boolean is64Bit() {
+            return this == X64 || this == AMD64 || this == ARM64 || this == X86_64 || this == AARCH64 || this == PPC64 || this == PPC64EL || this == RISCV64;
+        }
+
         public String key() {
             return this.key;
         }

src/main/java/net/minecraftforge/java_provisioner/DiscoMain.java

@@ -22,7 +22,7 @@ public static void main(String[] args) throws Exception {
         parser.allowsUnrecognizedOptions();
         OptionSpec<Void> helpO = parser.accepts("help", "Displays this help message and exits");
 
-        parser.accepts("disco-main", "Instructs the executable jar to use the DiscoMain entry point");
+        parser.accepts("disco-main", "Use the DiscoMain entry point");
 
         OptionSpec<File> cacheO = parser.accepts("cache",
                 "Directory to store data needed for this program")

src/main/java/net/minecraftforge/java_provisioner/JavaDirectoryLocator.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+package net.minecraftforge.java_provisioner;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import net.minecraftforge.java_provisioner.Disco.Arch;
+import net.minecraftforge.java_provisioner.api.IJavaInstall;
+import net.minecraftforge.java_provisioner.util.OS;
+import net.minecraftforge.java_provisioner.util.ProcessUtils;
+
+/*
+ * Attempts to find the java install from specific folders.
+ * Will search the folder, and immediate sub-folders.
+ */
+public class JavaDirectoryLocator extends JavaHomeLocator {
+    private final Collection<File> paths;
+
+    private static Collection<File> guesses() {
+        Collection<File> ret = new ArrayList<>();
+        if (OS.CURRENT == OS.WINDOWS) { // Windows
+            File[] roots = File.listRoots();
+            for(int i = 0; i < roots.length ; i++) {
+                ret.add(new File(roots[i], "Program Files\\Java"));
+                if (Arch.CURRENT.is64Bit())
+                    ret.add(new File(roots[i], "Program Files (x86)\\Java"));
+            }
+        } else if (OS.CURRENT == OS.OSX) { // Mac
+            ret.add(new File("/Library/Java/JavaVirtualMachines"));
+        } else { // Linux
+            ret.add(new File("/usr/java"));
+            ret.add(new File("/usr/lib/jvm"));
+            ret.add(new File("/usr/lib64/jvm"));
+            ret.add(new File("/usr/local/"));
+            ret.add(new File("/opt"));
+            ret.add(new File("/app/jdk"));
+            ret.add(new File("/opt/jdk"));
+            ret.add(new File("/opt/jdks"));
+        }
+
+        ret.removeIf(f -> !f.exists() || !f.isDirectory());
+
+        return ret;
+    }
+
+
+    public JavaDirectoryLocator() {
+        this(guesses());
+    }
+
+    public JavaDirectoryLocator(Collection<File> paths) {
+        this.paths = expand(paths);
+    }
+
+    private Collection<File> expand(Collection<File> files) {
+        Collection<File> ret = new ArrayList<>();
+        String exe = "bin/java" + OS.CURRENT.exe();
+        for (File file : files) {
+            if (new File(file, exe).exists())
+                ret.add(file);
+            else {
+                File[] subFiles = file.listFiles();
+                if (subFiles != null) {
+                    for (File subFile : subFiles) {
+                        if (subFile.isDirectory() && new File(subFile, exe).exists())
+                            ret.add(subFile);
+                    }
+                }
+            }
+        }
+        return ret;
+    }
+
+    @Override
+    public File find(int version) {
+        for (File path : paths) {
+            IJavaInstall result = fromPath(path);
+            if (result != null && result.majorVersion() == version)
+                return result.home();
+        }
+        return null;
+    }
+
+    @Override
+    public List<IJavaInstall> findAll() {
+        List<IJavaInstall> ret = new ArrayList<>();
+        for (File path : paths) {
+            IJavaInstall result = fromPath(path);
+            if (result != null)
+                ret.add(result);
+        }
+        return ret;
+    }
+}

src/main/java/net/minecraftforge/java_provisioner/Main.java

@@ -63,6 +63,7 @@ public static void main(String[] args) throws Exception {
         List<IJavaLocator> locators = new ArrayList<>();
         locators.add(new JavaHomeLocator());
         locators.add(new GradleLocator());
+        locators.add(new JavaDirectoryLocator());
         locators.add(disco);
 
         if (options.has(testO)) {

src/main/java/net/minecraftforge/java_provisioner/api/IJavaLocator.java

@@ -5,10 +5,12 @@
 package net.minecraftforge.java_provisioner.api;
 
 import java.io.File;
+import java.util.Arrays;
 import java.util.List;
 
 import net.minecraftforge.java_provisioner.DiscoLocator;
 import net.minecraftforge.java_provisioner.GradleLocator;
+import net.minecraftforge.java_provisioner.JavaDirectoryLocator;
 import net.minecraftforge.java_provisioner.JavaHomeLocator;
 
 public interface IJavaLocator {
@@ -58,6 +60,20 @@ static IJavaLocator home() {
         return new JavaHomeLocator();
     }
 
+    /**
+     * Returns a locator that searches a set of default 'guessed' directories based on OS.
+     */
+    static IJavaLocator paths() {
+        return new JavaDirectoryLocator();
+    }
+
+    /**
+     * Returns a locator that searches the specified directories, and immediate sub-directories.
+     */
+    static IJavaLocator paths(File... dirs) {
+        return new JavaDirectoryLocator(Arrays.asList(dirs));
+    }
+
     /**
      * Returns a new locator that implements the Disco API, using the specified directory as its download cache.
      */