问题描述
可能重复:
整数包装器对象仅共享相同的实例在值 127 以内?
我从 Khalid Mughal SCJP 复制了以下程序片段，但我无法
理解输出.
I have copied the following program snippet from the Khalid Mughal SCJP, but I am unable to
understand the output.
public class RQ200_60 {
public static void main(String[] args) {
Integer i = -10;
Integer j = -10;
System.out.print(i==j); // output: true -- why true?
System.out.print(i.equals(j)); // output: true
Integer n = 128;
Integer m = 128;
System.out.print(n==m); // output: false
System.out.print(n.equals(m)); // output: true
}
}
上面的程序为第一个打印语句给出了输出 true，但它应该给出 false，因为它是与 == 关系运算符的引用比较.但是第三次打印给出了错误，我不明白这种不一致.
The above program giving output true for the first print statement but it supposed to give false because it is reference comparison with == relational operator. But third print gives false and I don't understand this inconsistency.
非常感谢您的解释！
推荐答案
在第一种情况下，对象 i 和 j 都指向同一个缓存对象.默认情况下，-128 到 127 之间的范围被缓存为 Integer 对象.我们可以使用 JVM arguments
In the first case, both the objects i and j are pointing to the same cached object. By default, the range between -128 and 127 are cached as Integer Object. We can increase the range using JVM arguments
这篇关于为什么 == 对于某些 Integer 对象为真?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！