@svanloon The same API is available in Aspose.Words for Java starting from 21.12 version. We will fix the corresponding section in Java version API references. You can use this feature using the code like the following:
// Prepare font sources and generate font search cache beforehand.
FileFontSource fileSource = new FileFontSource(filePath, fileSourcePriority, fileSourceKey);
MemoryFontSource memorySource = new MemoryFontSource(fontData, memorySourcePriority, memorySourceKey);
StreamFontSource streamSource = new SteamFontSourceMemoryImpl(streamSourcePriority, streamSourceKey);
FontSettings settings = new FontSettings();
settings.setFontsSources(new FontSourceBase[] { fileSource, memorySource, streamSource });
settings.saveSearchCache(cacheOutputStream);
// Set font sources and load search cache before processing documents. Note that sources should be the same as when saving font search cache.
FileFontSource fileSource = new FileFontSource(filePath, fileSourcePriority, fileSourceKey);
MemoryFontSource memorySource = new MemoryFontSource(fontData, memorySourcePriority, memorySourceKey);
StreamFontSource streamSource = new SteamFontSourceMemoryImpl(streamSourcePriority, streamSourceKey);
FontSettings settings = new FontSettings();
settings.setFontsSources(new FontSourceBase[] { fileSource, memorySource, streamSource }, cacheInputStream);