JAVA 8

EARLIER:
Collections.sort(inventory, new Comparator() {
    public int compare(Apple a1, Apple a2){
       return a1.getWeight().compareTo(a2.getWeight());
    }
});

JAVA 8:
inventory.sort(comparing(Apple::getWeight));

EARLIER:
File[] hiddenFiles = new File(".").listFiles(new FileFilter() {
    public boolean accept(File file) {
        return file.isHidden();
    }
});

JAVA 8:
File[] hiddenFiles = new File(".").listFiles(File::isHidden);