A. Exchanging two numbers
two. Given three numbers, seeking the maximum and minimum
three basic knowledge variables.
1. integer variable int
int num = 10;
system.out.println(num);In Java, an int variable is four bytes and operating systems not directly related to the range of 4 bytes of data is -2 ^ 31 -> 2 ^ 31-1, it is about -21 billion and + 2.1 billion. in order to express more data, java provides a long type.
2. long long integer variable
long num = 10L;
system.out.println(num); Java, 8 bytes long type of data represented by the range -2 ^ 63 -> 2 ^ 63-1, far beyond an int.
3. The double-precision floating-point variables double
double num = 1.0;
system.out.println(num);Although the Java double is 8 bytes, but the great difference between the integer and floating point memory layout of the data can not be simply represented by a range of 2 ^ n form. Java memory layout of a double standard IEEE 754 compliance (C and languages), try to use the limited memory space may be infinite decimal representation, there is bound to be a certain degree of accuracy error.
4. single-precision floating-point variables
float num = 1.0F;
system.out,println(num);fl oat type accounted for four bytes in Java, also comply with the IEEE 754 standard. Due to the small data accuracy range indicated generally use floating-point numbers are priorities double, do not recommend the use of fl oat on the project.
The character type variable
char = 'A';
system.out,println(num);In java, you can use a character representation of a character such as: char = 'ah'; NOTE: The error may occur while performing, so we should javac time,
plus utf8 the -encoding.
6. byte type variable
byte value = 0;
system.out,println(value);Byte integer type is represented by only one byte, represents a smaller range (-128 -> +127)., And the type byte character type unrelated
7. short integer variable
short value = 0;
system.out.println(value);short occupies 2 bytes, the data range indicated -32768 -> 32767 2. This represents the range of relatively small, generally not recommended
8. boolean variable
boolean value = ture;
system.out.prinln(value);boolean type of variable only two values, true for true, false false representation. Java's boolean type int and can not be converted to each other, there is no 1 for true, 0 for such usage false. boolean achieve some type of JVM is accounted for 1 bytes, some of which are accounted for a bit, this is not clearly defined.
9. string variable type
some characters are put together to form the string
String name = "zhangsan";
System.out.println(name);
Java several characters in double quotes + represents manner string literals. Above different types, String not a basic type, but the reference type.
String operation + represents string concatenation, and the string may be an integer splice.
