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| package io.github.binglau;
import java.util.function.Supplier;
public final class LazyLoad {
private LazyLoad() {
}
private static class Holder {
private static final LazyLoad INSTANCE = new LazyLoad();
}
public static final LazyLoad getInstance() {
return Holder.INSTANCE;
}
private Supplier<Heavy> heavy = this::createAndCacheHeavy;
private Normal normal = new Normal();
public Heavy getHeavy() {
return heavy.get();
}
public Normal getNormal() {
return normal;
}
private synchronized Heavy createAndCacheHeavy() {
class HeavyFactory implements Supplier<Heavy> {
private final Heavy heavyInstance = new Heavy();
@Override
public Heavy get() {
return heavyInstance;
}
}
if (!HeavyFactory.class.isInstance(heavy)) {
heavy = new HeavyFactory();
}
return heavy.get();
}
public static void main(String[] args) throws InterruptedException {
LazyLoad.getInstance().getNormal();
LazyLoad.getInstance().getHeavy();
}
}
class Heavy {
public Heavy() {
System.out.println("Creating Heavy ...");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("... Heavy created");
}
}
class Normal {
public Normal() {
System.out.println("Creating Normal ...");
System.out.println("... Normal created");
}
}
|