multithreaded stamp loading

src/main/java/de/ph87/kindermalen/CONFIG.java

@@ -14,4 +14,6 @@ public class CONFIG {
 
   public static final int STAMP_BUTTON_SIZE = 75;
 
+  public static final int STAMP_BUTTON_ICON_REAL_SIZE = STAMP_BUTTON_SIZE - STROKE_HIGHLIGHT_WIDTH * 2;
+
 }

src/main/java/de/ph87/kindermalen/tools/tool/stamp/Stamp.java

@@ -11,6 +11,7 @@ import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 
+import static de.ph87.kindermalen.CONFIG.STAMP_BUTTON_ICON_REAL_SIZE;
 import static de.ph87.kindermalen.util.ImageHelper.RESIZE;
 
 @Slf4j
@@ -30,6 +31,7 @@ public class Stamp {
     this.name = file.getName().substring(0, file.getName().lastIndexOf("."));
     this.file = file;
     this.original = ImageIO.read(file);
+    getSize(STAMP_BUTTON_ICON_REAL_SIZE);
     log.info("Stamp loaded: {}", this);
   }
 

src/main/java/de/ph87/kindermalen/tools/tool/stamp/StampButton.java

@@ -30,7 +30,7 @@ public class StampButton extends JPanel {
     MouseListener.onRelease(this, this::onRelease);
     MouseListener.onEnter(this, this::onEnter);
     MouseListener.onExit(this, this::onExit);
-    icon = stamp.getSize(STAMP_BUTTON_SIZE - STROKE_HIGHLIGHT_WIDTH * 2);
+    icon = stamp.getSize(STAMP_BUTTON_ICON_REAL_SIZE);
     position = new Point((STAMP_BUTTON_SIZE - icon.getWidth()) / 2, (STAMP_BUTTON_SIZE - icon.getHeight()) / 2);
   }
 

src/main/java/de/ph87/kindermalen/tools/tool/stamp/StampTool.java

@@ -2,6 +2,7 @@ package de.ph87.kindermalen.tools.tool.stamp;
 
 import de.ph87.kindermalen.drawing.Drawing;
 import de.ph87.kindermalen.tools.tool.Tool;
+import de.ph87.kindermalen.util.Batch;
 import de.ph87.kindermalen.util.Vector;
 import lombok.Getter;
 import lombok.Setter;
@@ -11,8 +12,10 @@ import lombok.extern.slf4j.Slf4j;
 import java.awt.image.BufferedImage;
 import java.io.File;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.List;
-import java.util.Objects;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 import static de.ph87.kindermalen.util.FileHelper.SCAN_FILES;
 import static de.ph87.kindermalen.util.ImageHelper.ALPHA;
@@ -25,7 +28,7 @@ public class StampTool extends Tool {
 
   private static final File STAMPS_DIR = new File("./data/stamps");
 
-  private final List<Stamp> stamps;
+  private List<Stamp> stamps = new ArrayList<>();
 
   @Setter
   private Stamp stamp = null;
@@ -43,7 +46,12 @@ public class StampTool extends Tool {
 
   public StampTool() {
     super("Stempel");
-    stamps = SCAN_FILES(STAMPS_DIR).stream().map(this::load).filter(Objects::nonNull).toList();
+    final Stream<Supplier<Stamp>> runnables = SCAN_FILES(STAMPS_DIR).stream().map(stamp -> () -> StampTool.this.load(stamp));
+    try {
+      stamps = new Batch<>(runnables.toList()).join();
+    } catch (InterruptedException e) {
+      log.error(e.toString());
+    }
     if (stamp == null && !stamps.isEmpty()) {
       setStamp(stamps.get(0));
     }

src/main/java/de/ph87/kindermalen/util/Batch.java

@@ -0,0 +1,80 @@
+package de.ph87.kindermalen.util;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Supplier;
+
+@Slf4j
+public class Batch<T> {
+
+  private final List<Supplier<T>> suppliers;
+
+  private final Set<Thread> threads = new HashSet<>();
+
+  private boolean stop = false;
+
+  private final List<T> results = new ArrayList<>();
+
+  public Batch(final List<Supplier<T>> suppliers) {
+    this.suppliers = new ArrayList<>(suppliers);
+    synchronized (threads) {
+      for (int i = 0; i < Runtime.getRuntime().availableProcessors(); i++) {
+        final Thread thread = new Thread(this::threadMain, "BATCH-%03d".formatted(i));
+        threads.add(thread);
+        thread.start();
+      }
+    }
+  }
+
+  public void stop() {
+    synchronized (threads) {
+      stop = true;
+      threads.notifyAll();
+    }
+  }
+
+  public List<T> join() throws InterruptedException {
+    synchronized (threads) {
+      while (!threads.isEmpty()) {
+        threads.wait();
+      }
+      return results;
+    }
+  }
+
+  private void threadMain() {
+    try {
+      log.debug("Started");
+      while (true) {
+        final Supplier<T> supplier = getNext();
+        if (supplier == null) {
+          return;
+        }
+        final T result = supplier.get();
+        synchronized (results) {
+          results.add(result);
+        }
+      }
+    } finally {
+      synchronized (threads) {
+        threads.remove(Thread.currentThread());
+        threads.notifyAll();
+        log.debug("Terminated");
+      }
+    }
+  }
+
+  private Supplier<T> getNext() {
+    synchronized (threads) {
+      if (stop || suppliers.isEmpty()) {
+        return null;
+      }
+      return suppliers.remove(0);
+    }
+  }
+
+}