java – 盒装布尔值的等价

快速提问：是否保证此代码始终显示为真？

Boolean b1 = true;
Boolean b2 = true;
System.out.println(b1 == b2);

拳击布尔似乎总是导致相同的布尔对象,但我找不到太多关于JLS中的盒装布尔相等的信息.相反,它甚至似乎暗示拳击应该创建新对象,甚至可能导致OOM异常.

你的想法是什么？

解决方法:

从Java Language Specification on Boxing Conversion

Boxing conversion converts expressions of primitive type to
corresponding expressions of reference type. Specifically, the
following nine conversions are called the boxing conversions:

• From type boolean to type Boolean

[…]

If the value p being boxed is an integer literal of type int between
-128 and 127 inclusive (§3.10.1), or the boolean literal true or false (§3.10.3), or a character literal between '\u0000' and '\u007f'
inclusive (§3.10.4), then let a and b be the results of any two boxing
conversions of p. It is always the case that a == b.

这相对简单就像implemented那样

/**
 * The {@code Boolean} object corresponding to the primitive
 * value {@code true}.
 */
public static final Boolean TRUE = new Boolean(true);

/**
 * The {@code Boolean} object corresponding to the primitive
 * value {@code false}.
 */
public static final Boolean FALSE = new Boolean(false);

public static Boolean valueOf(boolean b) {
    return (b ? TRUE : FALSE);
}

标签：java,autoboxing,primitive
来源： https://codeday.me/bug/20190716/1476523.html