Data types in java

byte

• 8bit
• signed
• -128 to 127

short

• 16bit
• signed
• -32768 to 32767

int

• 32bit
• signed (since Java 8 it can be used to represent unsigned)
• -2³¹ to 2³¹-1

long

• 64bit
• signed (since Java 8 it can be used to represent unsigned)
• -2⁶³ to 2⁶³-1

float

• Single precision 32bit
• End with F or f

double

• Double precision 64bit
• End with D or d

boolean

• Only two values (true / false)

char

• Single 16bit unicode charactor (UTF 16)
• '\u0000' to '\uffff' (0 to 65535)

Here you can try this program to understand about java data types. 

public class DataTypes {

 public static void main(String[] args) {

  byte b = 10;
  short s = 5478;
  int i = 9978456;
  long l = 12547893533245625L;
  float f = 3.142f;
  double d = 1.0000000002125d;
  char c1 = 'A';
  char c2 = '\u0024';
  String st = "This is String";

  System.out.println("byte: " + b);
  System.out.println("short: " + s);
  System.out.println("int: " + i);
  System.out.println("long: " + l);
  System.out.println("float: " + f);
  System.out.println("double: " + d);
  System.out.println("char: " + c1);
  System.out.println("char unicode: " + c2);
  System.out.println("String: " + st);
 }
}

Type casting

Upward casting

 

 

  This method is implicit and reliable.

  There is the way to convert.

           int i = 10 ;

           double d = i ;  
   

public class DataTypes {

 public static void main(String[] args) {

  int i = 100;
  double d = i;
  System.out.println(d);
 }
}

Downward casting 

In this situating you can’t cast like upward method,If you try that way, it will give a compile time error.    

   double d = 3.14;

   int I = d; 

So you have to cast in this way, Now output is 3.    

   

   double d = 3.14;

   int I = (int) d; 

Your result is 3, double is floating point data type, but int is integer type.That is why you got the answer 3 instead of other one.

Try this code,

public class DataTypes {

 public static void main(String[] args) {

  int i = 128;
  byte b = (byte) i;

  System.out.println(b);

 }
}

In this program your output is -128,

You may confuse from this answer. Thing is that, the range of byte is -128 to 127. When it exceeds the limit, its wraparound. Then the next value after 127 is -128. 

Special escape characters

• \b - backspace
• \n - new line
• \t - tab
• \f - form feed
• \r - carriage return
• \" - double quote
• \' - single quote
• \\  - backslash

Underscore character

• After Java SE 7, you can use underscore (_) character in numerical fields. 
• This can be used to separate numbers into groups to read easy.
• But you can use it at the beginning or at the end of the number.
• You cannot put underscore just before or after the F, D or L character.
• It cannot be used before or after the decimal sign.

public class DataTypes {

 public static void main(String[] args) {
  
  long num1 = 5642_1245_7845_5458L;
  float num2 = 3.14_15F;
  long num3 = 0xFF_AC_FA;
  
  System.out.println(num1);
  System.out.println(num2);
  System.out.println(num3);

 }
}

Default values of data types 

Try this code to check default values in java.

public class DataTypes {

 static byte b;
 static short s;
 static int i;
 static long l;
 static float f;
 static double d;
 static String str;
 static boolean bool;

 public static void main(String args[]) {

  System.out.println("byte : " + b);
  System.out.println("short : " + s);
  System.out.println("int : " + i);
  System.out.println("long : " + l);
  System.out.println("float : " + f);
  System.out.println("double : " + d);
  System.out.println("String :" + str);
  System.out.println("boolean : " + bool);
 }
}