JAVA - Data Types

DATA TYPES:

Java defines eight primitive types of data: byte, short, int, long, char, float, double, and boolean. The primitive types are also commonly referred to as simple types. These can be put in four groups:

•   Integers This group includes byte, short, int, and long, which are for whole-valued signed numbers.

•  Floating-point numbers This group includes float and double, which represent numbers with fractional precision

•  Characters This group includes char, which represents symbols in a character set, like letters and numbers.

• Boolean This group includes boolean, which is a special type for representing true/false values.

INTEGER :

Java defines four integer types: byte, short, int, and long. All of these are signed, positiveand negative values. Java does not support unsigned, positive-only integers.

Byte: The smallest integer type is byte. This is a signed 8-bit type that has a range from –128 to

127.

Short: short is a signed 16-bit type. It has a range from –32,768 to 32,767.

Int: The most commonly used integer type is int. It is a signed 32-bit type that has a range from

–2,147,483,648 to 2,147,483,647.

Long: long is a signed 64-bit type and is useful for those occasions where an int type is not large enough to hold the desired value. The range of a long is quite large

Floating-Point Types

Floating-point numbers, also known as real numbers, are used when evaluating expressions that require fractional precision.

Float: The type float specifies a single-precision value that uses 32 bits of storage

Double: Double precision, as denoted by the double keyword, uses 64 bits to store a value. 

Characters

In Java, the data type used to store characters is char. Java char is a 16-bit type. The range of a char is 0 to 65,536. There are no negative chars.

Booleans

Java has a primitive type, called boolean, for logical values. It can have only one of two possible values, true or false.

Type Conversion and Casting

it is fairly common to assign a value of one type to a variable of another type which is known as casting.

Java’s Automatic Conversions

When one type of data is assigned to another type of variable, an automatic type conversion will take place if the following two conditions are met:

•  The two types are compatible.

•  The destination type is larger than the source type.

When these two conditions are met, a widening conversion takes place. For example, the int type is always large enough to hold all valid byte values, so no explicit cast statement is required.

if you want to assign an int value to a byte variable. This conversion will not be performed automatically, because a byte is smaller than an int. This kind of conversion is sometimes called a narrowing conversion, since you are explicitly making the value narrower so that it will fit into the target type. To create a conversion between two incompatible types, you must use a cast. A cast is simply an explicit type conversion. It has this general form:

(target-type) value int a;

byte b;

// ...

b = (byte) a;

Arrays: An array is a group of like-typed variables that are referred to by a common name. Arrays of any type can be created and may have one or more dimensions. Aspecific element in an array is accessed by its index.      type var-name[ ];

An Example for Multidimensional Array.

While we define an multidimensional array it is necessary to define the number of row but not the column values.

public class arrayl {

public static void main(String args[]){

int twoD[][]= new int[4][];

// Multidimensional array each row has variable column values. twoD[0]=new int[1];

twoD[1]=new int[2]; twoD[2]=new int[3]; twoD[3]=new int[4];

int i,j,k=0;

for(i=0;i<4;i++) for(j=0;j<i+1;j++){

twoD[i][j]=k; k++;

}

for(i=0;i<4;i++){ for(j=0;j<i+1;j++)

System.out.print(twoD[i][j] + " ");

System.out.println();

}

System.out.printf("the value of k is %d",k);

}

}