Java – comparing strings

Use == for primitive data types like int

If (mystring == null)

 

Use the equals() method to compare objects

Use .equals for strings  : if (a.equals(“cat”))

 

Java - Converting int to string

String myString = Integer.toString(my int value)

   or

String str = "" + i

 

Java - Converting String to int

int i = Integer.parseInt(str);

   or
int i = Integer.valueOf(str).intValue();

  

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 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 binstr = 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());
      }
}

 

hexadecimal (String) to integer :

int i = Integer.valueOf("B8DA3", 16).intValue();
   or

int i = Integer.parseInt("B8DA3", 16);    



ASCII code to String

int i = 64;

String aChar = new Character((char)i).toString();


integer to ASCII code (byte)

char c = 'A';

int i = (int) c; // i will have the value 65 decimal



integer to boolean

b = (i != 0);

 

boolean to integer

i = (b)?1:0;

 

 출처 : http://stuff.mit.edu/people/ele/Javaconversion.htm