Java SE: Programming Complete - 2

https://learn.oracle.com/ols/course/java-se-programming-complete/82508/85200

Primitive Types, Operators, and Flow Control Statements

Whole Numbers

• byte - 8 bits (1 byte)
• short - 16 bits (2 bytes)
• int - 32 bits (4 bytes)
• long - 64 bits (8 bytes)

  Default value is 0 or 0L

Floating point numbers

• float - 32 bits (4 bytes)
• double - 64 bits (8 bytes)

  Default value is 0.0 or 0.0F

Boolean

• boolean - true of false

  Default value is false

Character

• char - 16 bits (0 - 65535)

  default value ‘\u0000’ (\u means unicode)

Arithmetic Operations and Type Casting

• Smaller types are automatically casted to bigger types

  byte->short->char->int->long->float->double

• A bigger type value can’t be assigned to a smaller type variable without explicit type casting, beware of a possible overflow
• Resulting type of arithmetic operations on types smaller than int is an int; otherwise, the result is of a type of a largest participant. (not apply to ++ or --, which means short++ will still be a short)

Bitwise Operators

• Signed Left Shift << shifts each bit to the left by specified number of positions, fills low-order positions with 0 bit values.
• Sighned Right Shift >> shifts each bit to the right by specified number of positions.
• Unsigned Right Shift >>> same as above, but fills high-order positions with 0 bit values.

Flow Control Using switch Construct

• Switch expression must be of one of the following types: byte, short, int, char, String, enum
• If the switch expression did not match any of the cases, then the default case is executed. It doesn’t not have to be the last case in the sequence and it’s optional.

JShell

JShell was introduced in JDK 9 as part of Java Enhancement Proposal (JEP) 222 under project Kulla. Many programming languages, such as JavaScript, Python, Ruby, etc., provide easy-to-use, command-line tools for their execution, but Java was still missing such a utility. So, JDK 9 introduced the Java shell (JShell) tool.

https://developers.redhat.com/blog/2019/04/05/10-things-developers-need-to-know-about-jshell/