String to Integer

Integer entero = Integer.valueOf(cadena);
// o
int entero = Integer.parseInt(cadena);

Example:

Integer a = Integer.valueOf("900");
// o
int b = Integer.parseInt("900");

Integer to String

String cadena = Integer.toString(entero);
// o
String cadena = String.valueOf(entero);

Example:

String importe = Integer.toString(900);
// o
int entero = 900;
String mensaje = String.valueOf(entero);

char to String

String cadena = Character.toString(char);

Example:

char codigo = 'A';
String cadena = Character.toString(codigo);

String to char

char caracter = cadena.charAt(0); //Solo primer caracter

Example:

String codigo= "E";
char caracter = cadena.charAt(0);

String to Double

double doble = Double.parseDouble(cadena);

Example:

double doble = Double.parseDouble("900.1");

Double to String

String cadena = String.valueOf(doble);

Example:

double totalDoble = 900.5;
String totalString = String.valueOf(doble);

String to Float

float flotante = Float.parseFloat(cadena);

Example:

float importe = Float.parseFloat("900.5");

Float to String

String cadena = Float.toString(flotante);

Example:

String total = Float.toString(900.1f);

String to Boolean

Boolean boolean = Boolean.valueOf(cadena);
// o
boolean boolean = Boolean.parseBoolean(cadena);

Example:

Boolean boolean = Boolean.valueOf("true");
// o
boolean boolean = Boolean.parseBoolean("false");

Boolean to String

String cadena = String.valueOf(b);
// o
String cadena = Boolean.toString(b);

Example:

boolean b = true;
String cadena = String.valueOf(b);
// o
boolean b = false;
String cadena = Boolean.toString(b);

To do the following operation we will need to use the class Integerand its method "parseInt"as follows:

    String numCadena = "1";

int numEntero = Integer.parseInt(numCadena);

What problems can we have? So that the string not only contains numbers but also comes with spaces.

If the spaces come at the beginning or at the end, a simple trim will suffice to eliminate them, for example("1")

numCadena.trim();

If we have space between the numbers we should use the method

replaceAll (" 1 3 45 6")
numCadena.replaceAll(" ", "");

Once these simple steps have been carried out, we can work with integers.

PASS AN INT TO STRING (FROM INT TO STRING)

To pass from a basic type to a String object we have several possibilities, on the one hand, if you are a craftsman, you can simply concatenate an empty string to your integer:

    int numEntero = 4;

String numCadena= numEntero+"";

The correct way to perform this operation would be calling the method valueOfof the classString

int numEntero = 4;

String numCadena= String.valueOf(numEntero);

Another correct way to do it would be using the toString method of the Integer object as follows:

String numCadena= Integer.toString(numEntero);