Digit base
Integer expansion
How to deal with binary, decimal, octal and hexadecimal expressions of "10"?
Binary plus 0b
decimal system
Octal plus 0
Hex plus 0x
give an example:
int i = 10; int i1 = 010; //Octal 0 int i2 = 0x10; // Hex 0x 0 ~ 9 A ~ F int i3 = 0b10; System.out.println(i); System.out.println(i1); System.out.println(i2); System.out.println(i3);
Floating point extension
How to express banking business?
Floating point numbers are finite and discrete, so they are approximate, but close to but not equal to.
Therefore, it is better not to compare with floating-point numbers:
Therefore, it is better not to compare with floating-point numbers:
Therefore, it is better not to compare with floating-point numbers:
give an example:
float f = 0.1f; double d = 1.0/10; System.out.println(f==d); //false System.out.println(f); System.out.println(d); float d1 = 232333334444443f; float d2= d1 + 1; System.out.println(d2); System.out.println(d1==d2);
From the output result, f=d=0.1 F should be equal to d
d2=d1+1 D2 is not equal to D1;
However, according to the program judgment, f is not equal to d; d2 equals d1, which is why.
For the comparison of accurate data, we need to use the mathematical tool class: BigDecimal
Character expansion
All characters are essentially numbers. Cast characters into integer numbers.
give an example:
char c1 = 'a'; char c2 = 'in'; System.out.println(c1); System.out.println(c2); System.out.println((int)c1); //Cast line System.out.println((int)c2); //Cast line
//Code: byte 0 ~ 65536 of Unicode Table 2 to the 16th power of Excel 2; // Range of Unicode table: U0000 ~ UFFFF
There is a Unicode table in the character and number conversion as the "translation table"
The corresponding output can be viewed with the following instructions:
char c3 = '\u0061';//Escape character System.out.println(c3); //a
Digit base
Integer expansion
How to deal with binary, decimal, octal and hexadecimal expressions of "10"?
Binary plus 0b
decimal system
Octal plus 0
Hex plus 0x
give an example:
int i = 10; int i1 = 010; //Octal 0 int i2 = 0x10; // Hex 0x 0 ~ 9 A ~ F int i3 = 0b10; System.out.println(i); System.out.println(i1); System.out.println(i2); System.out.println(i3);
Floating point extension
How to express banking business?
Floating point numbers are finite and discrete, so they are approximate, but close to but not equal to.
Therefore, it is better not to compare with floating-point numbers:
Therefore, it is better not to compare with floating-point numbers:
Therefore, it is better not to compare with floating-point numbers:
give an example:
float f = 0.1f; double d = 1.0/10; System.out.println(f==d); //false System.out.println(f); System.out.println(d); float d1 = 232333334444443f; float d2= d1 + 1; System.out.println(d2); System.out.println(d1==d2);
From the output result, f=d=0.1 F should be equal to d
d2=d1+1 D2 is not equal to D1;
However, according to the program judgment, f is not equal to d; d2 equals d1, which is why.
For the comparison of accurate data, we need to use the mathematical tool class: BigDecimal
Character expansion
All characters are essentially numbers. Cast characters into integer numbers.
give an example:
char c1 = 'a'; char c2 = 'in'; System.out.println(c1); System.out.println(c2); System.out.println((int)c1); //Cast line System.out.println((int)c2); //Cast line
//Code: byte 0 ~ 65536 of Unicode Table 2 to the 16th power of Excel 2; // Range of Unicode table: U0000 ~ UFFFF
There is a Unicode table in the character and number conversion as the "translation table"
The corresponding output can be viewed with the following instructions:
char c3 = '\u0061';//Escape character System.out.println(c3); //a
Common escape characters include:
//Transfer character
// \t tab
// \n line feed
// \r enter
// \b backspace
System.out.println("Hello\tWorld");
Boolean extension
boolean flag = true;
if (flag==true) {} is the same as if (flag) {}.
Common escape characters include:
//Transfer character
// \t tab
// \n line feed
// \r enter
// \b backspace
System.out.println("Hello\tWorld");
Boolean extension
boolean flag = true;
if (flag==true) {} is the same as if (flag) {}.