So let’s look at a little bit of code, pretty simple, right
Execute:
Contrary to what most people think, many people are still struggling to decide whether all is true or all is false.
However, one is true and one is false. Why is this?
Some people don’t think at all, just open Baidu search to find the answer (all of them are chief software engineers of Baidu)
The.class file is generated for the JVM to load and execute, so we went to the.class file and decomcompiled it. When we compiled our code, the compiler mischievously (and slyly) added the valueOf method to the variable we declared, and the code looked like this:
Look at the implementation of the valueOf method
If the value is in the cache, the value is returned. If the value is not in the cache, a new object is returned. Consider the IntegerCache class:
This is an internal static class that can only be accessed inside the Integer class, which, when initialized, loads the JVM’s configuration, initializes the cache array with the configured value if any, and caches values between -128 and 127 otherwise.
Take a look at our previous code:
Conclusion: When comparing the values of two Integer objects, we must use equals instead of ==. There is no overloaded operator in Java, especially if you are moving to Java from other languages. I’ve covered equals in detail in other articles, Portal: Talk about Equals in Java
Consider the result of executing the following code:
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