Java basic Type Auto-boxing (autoboxing)

After the Java SE 1.5 release and later, the automatic boxing feature is available.

Auto-boxing, "wrapping" the underlying type into one type:

Basic Type-wrapper class

The following procedure triggers an automatic boxing process:

Integer count = 1;

Double amount = 2.0D

　　

From the Javadoc API, the wrapper class provides a way to manipulate the underlying type of encapsulation:

Type conversions, such as float-to-int

Comparison

...

It is worth noting that for values between [-128, 127], automatic boxing uses caching to provide memory efficiency.

That is, automatically boxing the value of the range, the resulting wrapper class memory address is not changed.

For example

Integer a = 129;

Integer B = 129;

System.out.println (A = = B);//Output True

Practice:

1, automatic boxing appears in the variable declaration;

2, consider the use of one of the scenarios, the basic types need to compare, type conversion and other operations;

3, if you need to compare the wrapper class = =, it is recommended to convert to the underlying type, and then proceed.

To avoid the effect of the cache value range [-128, 127] on = = Comparison results.

Java basic Type Auto-boxing (autoboxing)