Type |
Contains |
Default |
Size |
Range |
true or false | false | 1 bit | NA | |
Unicode character unsigned |
\u0000 | 16 bits or 2 bytes |
0 to 216-1 or \u0000 to \uFFFF |
|
Signed integer | 0 | 8 bit or 1 byte |
-27 to 27-1 or -128 to 127 |
|
Signed integer | 0 | 16 bit or 2 bytes |
-215 to 215-1 or -32768 to 32767 |
|
Signed integer | 0 | 32 bit or 4 bytes |
-231 to 231-1 or -2147483648 to 2147483647 |
|
Signed integer | 0 | 64 bit or 8 bytes |
-263 to 263-1 or -9223372036854775808 to 9223372036854775807 |
|
IEEE 754 floating point single-precision |
0.0f | 32 bit or 4 bytes |
�1.4E-45 to �3.4028235E+38 |
|
IEEE 754 floating point double-precision |
0.0 | 64 bit or 8 bytes |
�439E-324 to �1.7976931348623157E+308 |
A boolean type, a character type, four integer types, and two floating types.
The boolean type has two possible values, representing two states: on or off, yes or no, true or false. Java reserves the words true and false to represent these two boolean values.
To declare a boolean variable:
public class Test { boolean b; public static void main(String[] args) { System.out.println(new Test().b); // prints false // System.out.println(b);//You can't reach b, which is not static variable. } }
The char type represents Unicode characters. Its size is 16 bits long.
To declare a char variable, simple place it between single quotes(apostrophes):
You can use escape sequence to represent character literal.
'\uxxxx is Unicode escape sequence, where xxxx is for hexadecimal digits
'\xxx' is Latin-1 character, where xxx is an octal(base 8) number between 000 and 377.
Nonprinting ASCII character:
'\t' -- horizontal tab
'\b' -- backspace
'\n' -- newline
'\f' -- form feed
'\r' -- carriage return
public class Test { public static void main(String[] args) { char c = 'A'; char tab = '\t'; char nul = ' '; char aleph = '\u05D0'; char backslash = '\\'; char singleQuote ='\''; char doubleQuote = '\"'; System.out.println(c); //... } }You can't do these:
char nul = ''; char singleQuote = '''; char doubleQuote = '"'; char backslash = '\';
byte, short, int, long are called integer types. These four types differ only in the number of bits.
Literals for each type: byte, short and int are almost the same.
public class Test { public static void main(String[] args) { byte b = 127; // Min:-128 Max: 127 int i1 = 28; int i2 = 0x1c; //hexadecimal 28 int i3 = 034; // octal 28 int i4 = 0xCAFEBABE; //magic number used to identify Java class files long l1 = 12345L; //a long value long l2 = 12345l; //a long value long l3 = 0xffL; // a long value System.out.println(l3); } }You can't do these:
byte b = 128; short s = -32770; int i = 0xCAFEBABEFF;//too large if byte b1 = 127, b2 = 2; byte sum = b1 + b2; //not allowed, but System.out.println(b1+b2); //OK, because "+" in the .println() will promote byte or short to int automatically.
float and double data types represent real numbers. The float has at least 6 significant decimal digits and a double has at least 15 significant digits. The literals use a string of digits.
public class Test { public static void main(String[] args) { float f = 6.02e23f; //represents 6.02 x 1023 double d = 1e-6; // represents 1 x 10-6 double d2 = 123.4; //no problem to compile. //no exception thrown even if illegal operations double inf = 1/0; //infinity double neginf = -1/0; // -infinity double negzero = -1/inf; // negative zero double NaN = 0/0; //NaN--not a number } }To check whether a float or double value is NaN, you must use the Float.isNaN() and Double.isNaN() methods.
The String type is a class, not a primitive type. String literals contain a string of letters including escape sequences that can appear as char literals.
public class Test { public static void main(String[] args) { String s = "This is a test"; String s1 = "\nThis is the second line"; System.out.println(s+s1); } }
Wrapper classes are classes related primitives. Each primitive type has a corresponding wrapper class.
boolean -- Boolean char -- Character* byte -- Byte short -- Short int -- Integer* long -- Long float -- Float double -- Double