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package com.pdd.pop.ext.glassfish.grizzly.utils;
/**
* The object holder, which might be used for lazy object initialization.
*
* @author Alexey Stashok
*/
public abstract class Holder {
public static Holder staticHolder(final T value) {
return new Holder() {
@Override
public T get() {
return value;
}
};
}
public static IntHolder staticIntHolder(final int value) {
return new IntHolder() {
@Override
public int getInt() {
return value;
}
};
}
public static LazyHolder lazyHolder(final NullaryFunction factory) {
return new LazyHolder() {
@Override
protected T evaluate() {
return factory.evaluate();
}
};
}
public static LazyIntHolder lazyIntHolder(final NullaryFunction factory) {
return new LazyIntHolder() {
@Override
protected int evaluate() {
return factory.evaluate();
}
};
}
public abstract E get();
@Override
public String toString() {
final E obj = get();
return obj != null ? "{" + obj + "}" : null;
}
public static abstract class LazyHolder extends Holder {
private volatile boolean isSet;
private E value;
@Override
public final E get() {
if (isSet) {
return value;
}
synchronized (this) {
if (!isSet) {
value = evaluate();
isSet = true;
}
}
return value;
}
protected abstract E evaluate();
}
public static abstract class IntHolder extends Holder {
@Override
public final Integer get() {
return getInt();
}
public abstract int getInt();
}
public static abstract class LazyIntHolder extends IntHolder {
private volatile boolean isSet;
private int value;
@Override
public final int getInt() {
if (isSet) {
return value;
}
synchronized (this) {
if (!isSet) {
value = evaluate();
isSet = true;
}
}
return value;
}
protected abstract int evaluate();
}
}