refactor(java): modularize Java detection and management system

- Split monolithic java.rs (1089 lines) into focused modules
  - detection: Java installation discovery
  - validation: Version validation and requirements checking
  - priority: Installation selection priority logic
  - provider: Java download provider trait
  - providers: Provider implementations (Adoptium)
  - persistence: Cache and catalog management
- Add java_path_override field to Instance struct for per-instance Java configuration
- Export JavaInstallation at core module level

This refactoring improves maintainability and prepares for multi-vendor Java provider support.

Reviewed-by: Claude Sonnet 4.5

1 files changed, 41 insertions, 0 deletions

diff --git a/src-tauri/src/core/java/provider.rs b/src-tauri/src/core/java/provider.rs
new file mode 100644
index 0000000..0f9d78a
--- /dev/null
+++ b/src-tauri/src/core/java/provider.rs
@@ -0,0 +1,41 @@
+use crate::core::java::{ImageType, JavaCatalog, JavaDownloadInfo};
+use tauri::AppHandle;
+
+/// Trait for Java download providers (Adoptium, Temurin, Corretto, etc.)
+/// 
+/// Implements SOLID principles:
+/// - Single Responsibility: Each provider handles one download source
+/// - Open/Closed: New providers can be added without modifying existing code
+/// - Liskov Substitution: All providers are interchangeable
+/// - Interface Segregation: Minimal required methods
+/// - Dependency Inversion: Code depends on trait, not concrete implementations
+pub trait JavaProvider: Send + Sync {
+    /// Fetch the Java catalog (all available versions for this provider)
+    async fn fetch_catalog(
+        &self,
+        app_handle: &AppHandle,
+        force_refresh: bool,
+    ) -> Result<JavaCatalog, String>;
+
+    /// Fetch a specific Java release
+    async fn fetch_release(
+        &self,
+        major_version: u32,
+        image_type: ImageType,
+    ) -> Result<JavaDownloadInfo, String>;
+
+    /// Get list of available major versions
+    async fn available_versions(&self) -> Result<Vec<u32>, String>;
+
+    /// Get provider name (e.g., "adoptium", "corretto")
+    fn provider_name(&self) -> &'static str;
+
+    /// Get OS name for this provider's API
+    fn os_name(&self) -> &'static str;
+
+    /// Get architecture name for this provider's API
+    fn arch_name(&self) -> &'static str;
+
+    /// Get installation directory prefix (e.g., "temurin", "corretto")
+    fn install_prefix(&self) -> &'static str;
+}