de.larssh.utils.Finals Maven / Gradle / Ivy
// Generated by delombok at Sat Apr 03 10:50:23 UTC 2021
package de.larssh.utils;
import java.util.function.Supplier;
import edu.umd.cs.findbugs.annotations.Nullable;
/**
* This class contains helper methods for final fields.
*/
public final class Finals {
/**
* Returns {@code value} unchanged. This prevents compilers from inlining
* constants (static final fields). Depending classes referring to the constant
* do not need to be recompiled if the constant value changes.
*
*
* Inlining affects primitive data types and strings.
*
*
* Usage example:
*
public static final String CONSTANT_FIELD = constant("constant value");
*
* @param return type
* @param value value
* @return value
*/
public static T constant(final T value) {
return value;
}
/**
* Returns a new {@link Supplier} that calculates its return value at most one
* time. Therefore it can be used to create lazy fields.
*
*
* This implementation is synchronized. {@code supplier} is guaranteed to be
* called at max once.
*
* @param return type
* @param supplier value supplier
* @return value
*/
public static Supplier lazy(final Supplier supplier) {
return new CachedSupplier<>(supplier);
}
/**
* {@link Supplier} implementation proxying another supplier while calculating
* its return value at most one time.
*
*
* Threads are synchronized upon calling the wrapped supplier.
*
* @param return type
*/
private static class CachedSupplier implements Supplier {
/**
* Wrapped supplier
*
* @return wrapped supplier
*/
private final Supplier supplier;
/**
* Cached value or empty optional
*
* @return cached value or empty optional
*/
@Nullable
private volatile T value = null;
/**
* Object used for locking
*/
private final Object lock = new Object();
/** {@inheritDoc} */
@Override
public T get() {
synchronized (lock) {
if (value == null) {
value = supplier.get();
}
}
return Nullables.orElseThrow(value);
}
@java.lang.SuppressWarnings("all")
@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(justification = "generated code")
@lombok.Generated
public CachedSupplier(final Supplier supplier) {
this.supplier = supplier;
}
}
@java.lang.SuppressWarnings("all")
@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(justification = "generated code")
@lombok.Generated
private Finals() {
throw new java.lang.UnsupportedOperationException("This is a utility class and cannot be instantiated");
}
}