"Java" Java basics

1. The difference between int and integer

int is the basic data type, and integer is a reference data type.

e.g:

int num = 100; Not an Object

Integer i = 100; is an object

Num. Properties and methods are not out of order

I. Point-out properties and methods

Integer is the boxed class of the integer type, which can be boxed and unboxing

i = num; Automatic Boxing

num = i; Automatic unpacking

Boxing--"Converting a value type to a reference type

Unpacking-"Converting a reference type to a value type"

-Integer is an int type encapsulation class, int is not an object       base type ->integer is an object   reference type

2, = = and equals () the difference?

for = =, if both sides are numeric values, indicate whether the values are equal, if the two days are reference types, the objects are the same. ->equals () to determine whether the contents of the two objects are the same.

 String s1 = "Hello" ; string s2  = new  String ("Hello"  = new  String ("Hello"  = = s2); //  SYSTEM.OUT.PRINTLN (s2 = = s3); //  system.out.println (s1.equals (S2));  //  System.out.println (S2.equals (S3)); //  

string S1 = "Hello"= "Hello"new String ("Hello"//  true//  false//  true//   True

"Java" Java basics