Automatic boxing and unboxing

1. Automatic packing

　　Integer i = 123;

2. Automatic unpacking

　　int i = new Integer(123);

3. Pay attention

　　Numbers between Integer objects [-128, 127] are still treated as primitive data types, for example

　　Integer i1 = 100;

　　Integer i2 = 100;

　　System.out.println(i1 == 12); //The result is true at this time