Java introduction, environment construction and structured program

Java Chapter 1:

The difference between JDK and JRE: JRE (Java Runtime Environment) Java runtime environment Some programs need a Java environment to run, so JRE is only used by clients.

When JDK (Java Development Kit) develops Java program components, you need to manually configure path variables, including JRE.

Java Chapter 2:

>>>Unsigned right shift A>>>B means to move the complement of A to the right by B bits, and add 0 to the left, while A>>B is to add the highest bit to the left.

foreach usage:

for(String st:vs)
  {
   System.out.println(st);
  }

You can directly traverse the Vector<String> object vs the value.

The vs here can be an array, vector, hash, linked list, etc.