bayou.util

Interface Var<T>

public interface Var<T>

A variable that can be read from and written to.

See get() and set(T) methods.

The set() method may opt to throw RuntimeException for whatever reason.

hashCode(), equals(), toString()

These methods on a subclass must have the following semantics

    public int hashCode()
    {
        return Objects.hashCode(get());
    }
    public boolean equals(Object obj)
    {
        return (obj instanceof Var) && Objects.equals(this.get(), ((Var<?>)obj).get());
    }
    public String toString()
    {
        return String.valueOf(get());
    }
 

A subclass can simply copy&paste these lines. Unfortunately they cannot be default methods on this interface.

Method Summary

Abstract Methods
T	get() Read the value of this Var.
T	set(T value) Set the value of this Var, then return the value.
Static Methods
<T> Var<T>	of(Supplier<? extends T> getter, Consumer<? super T> setter) Create a Var with the getter and setter.
<T> Var<T>	init(T initValue) Create a simple Var with the initial value.
<T> Var<T>	init(T initValue, Consumer<? super T> validator) Create a Var with a validator.

Method Detail

get

T get()

Read the value of this Var.

set

T set(T value)
throws RuntimeException

Set the value of this Var, then return the value.

Note that the new value, not the old one, is returned. This is to be consistent with the semantics of Java assignment expression.

Returns:

the same `value`

Throws:

RuntimeException - if the value cannot be set, for whatever reason.

of

static <T> Var<T> of(Supplier<? extends T> getter,
                     Consumer<? super T> setter)

Create a Var with the getter and setter.

The get() and set() methods of the Var simply forward to the getter and setter.

init

static <T> Var<T> init(T initValue)

Create a simple Var with the initial value.

The get() and set() methods of the Var are just like read/write a non-volatile field.

init

static <T> Var<T> init(T initValue,
                       Consumer<? super T> validator)
                throws RuntimeException

Create a Var with a validator.

The set(value) methods of the Var will first call `validator.accept(value)`; if the validator throws RuntimeException, set(value) throws the same exception. Other than that, the get() and set() methods are just like read/write a non-volatile field.

The initValue is also checked by the validator; if the validator throws RuntimeException, this method throws the same exception.

Throws:

RuntimeException