Chapter 2 knowledge points

1. The String constant uses double quotation marks as the separator of the string.

Format: it can contain numbers, punctuation marks, null, and other special characters,

2. What are the similarities and differences between the print and println methods?

A: Similarities: the print and println methods represent the two services provided by the system. Out object.

Difference: the print cursor will not move to the next line

The println cursor moves to the next line.

3. String concatenation operator?

A: The String concatenation operator is "+ ".

4. Escape sequences are used to indicate special characters that may cause compilation errors.

Escape Sequence in Java

5. variables, assignments, and constants

A: A variable represents the memory unit for storing data. The variable name is the symbolic address of the memory unit.

 

Eg: int total; // declare an integer variable

Double num1, num2 = 4.356, num3; // declare a Boolean variable

Char letter = 'A', digit = '7'; // declare a character variable

Final int max = 45; // declare a constant integer variable

Value assignment: Reading data does not change its value in memory, but the value assignment statement overwrites the old data.

 

Constant: a specific value is saved during existence.

Reserved word of a constant: Final

Variable name of a constant: All values must be in uppercase.

// Declare a constant integer variable and assign 27 values to the variable

Eg: Final int max_occupancy = 27;

6. Basic Data Types

Eight basic data types: Four integer types, two floating point types, complex type and boolean type.

Four integer types: byte, short, Int, and long character type: Char. Note: single quotes are used to indicate the character constants such as 'B ',';',''.....

Two floating point types: float and double Boolean: Boolean. Note: The result is only "Turn" or "false ".

 

Chapter 2 knowledge points