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Convert from type X to type YTag(s): String/Number


integer to String : 
int i = 42;
String str = Integer.toString(i);
   or
String str = "" + i
double to String : 
String str = Double.toString(i);
long to String : 
String str = Long.toString(l);
float to String : 
String str = Float.toString(f);

String to integer : 
   str = "25";
   int i = Integer.valueOf(str).intValue();
   or
   int i = Integer.parseInt(str);
String to double : 
Double d = Double.valueOf(str).doubleValue();
String to long : 
   long l = Long.valueOf(str).longValue();
   or
   Long l = Long.parseLong(str);
String to float : 
Float f = Float.valueOf(str).floatValue();
decimal to binary : 
int i = 42;
String bin = Integer.toBinaryString(i);
decimal to hexadecimal : 
   int i = 42;
   String hexstr = Integer.toString(i, 16);

   or
   String hexstr = Integer.toHexString(i);

   or (with leading zeroes and uppercase)
   public class Hex {
     public static void main(String args[]){
       int i = 42;
       System.out.print
         (Integer.toHexString( 0x10000 | i).substring(1).toUpperCase());
     }
   }
Byte array to hexadecimal string:
See this How-to

hexadecimal (String) to integer : 

int i = Integer.valueOf("B8DA3", 16).intValue();
   or
int i = Integer.parseInt("B8DA3", 16);
char to String 
String s = String.valueOf('c');
integer to ASCII code (byte) 
char c = 'A';
int i  = (int) c; // i ==  65 DECIMAL
To extract Ascii codes from a String 
String test = "ABCD";
for ( int i = 0; i < test.length(); ++i ) {
   char c = test.charAt( i );
   int j = (int) c;
   System.out.println(j);
}
integer to boolean 
b = (i != 0);
// ex : 42 != 0 --> true
boolean to integer 
i = (b)?1:0;
// true --> 1
Note :To catch illegal number conversion, use the try/catch mechanism : 
try{
  i = Integer.parseInt(aString);
}
catch(NumberFormatException e) {
  ...
}