[Java] 절대 코더들도 까먹는 형변환 (int, double, long.. <->String)

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