Java String Conversion

In this chapter you will learn:

How to Convert boolean, char, double, float,int,long,object to String
How to Convert string case with locale
How to encode a string into byte array

Convert boolean, char, double, float,int,long,object to String

The following static methods from String class converts primitive types to String.

static String valueOf(boolean b) converts boolean to string
static String valueOf(char c) converts char to string
static String valueOf(char[] data) converts char array to string
static String valueOf(char[] data, int offset, int count) converts sub char array to string
static String valueOf(double d) converts double to string
static String valueOf(float f) converts float to string
static String valueOf(int i) converts int to string
static String valueOf(long l) converts long to string
static String valueOf(Object obj) converts Object to string

public class Main {
  public static void main(String[] argv) {
    String str = String.valueOf(123);/* jav  a 2  s  .c  om*/

    System.out.println(str);
  }
}

The output:

public class Main {
  public static void main(String args[]) {
    char charArray[] = { 'a', 'b', 'c', 'd', 'e', 'f' };
    boolean booleanValue = true;
    char characterValue = 'Z';
    int integerValue = 7;
    long longValue = 10000000000L; // L suffix indicates long
    float floatValue = 2.5f; // f indicates that 2.5 is a float
    double doubleValue = 3.3; // no suffix, double is default
    Object objectRef = "hello"; // assign string to an Object reference
/*from  jav a  2  s  .  c  o m*/
    System.out.printf("char array = %s\n", String.valueOf(charArray));
    System.out.printf("part of char array = %s\n", String.valueOf(charArray, 
                              3, 3));
    System.out.printf("boolean = %s\n", String.valueOf(booleanValue));
    System.out.printf("char = %s\n", String.valueOf(characterValue));
    System.out.printf("int = %s\n", String.valueOf(integerValue));
    System.out.printf("long = %s\n", String.valueOf(longValue));
    System.out.printf("float = %s\n", String.valueOf(floatValue));
    System.out.printf("double = %s\n", String.valueOf(doubleValue));
    System.out.printf("Object = %s\n", String.valueOf(objectRef));
  }
}

The output:

Convert string case with locale

We can use the following methods to change the case of a string. We can also choose a Locale during the changing. A locale is a settings for a specific languages or countries.

String toLowerCase() converts String to lower case using default locale.
String toLowerCase(Locale locale) converts String to lower case using given Locale.
String toUpperCase() converts String to upper case using default locale.
String toUpperCase(Locale locale) converts String to upper case using given Locale.

The following code defines a string first and then change its case to upper and lower.

public class Main {
  public static void main(String[] argv) {
    String str = "Demo2s.com";
    System.out.println(str.toLowerCase());
    System.out.println(str.toUpperCase());
//from j  a  v  a 2  s .com
  }
}

The output:

Convert string to byte array

Sometime we need to convert string value to byte array before we can transfer them through the network or save them to file or database. During the converting we can encode the string in specified charset.

byte[] getBytes() encodes String to byte array using default charset
byte[] getBytes(Charset charset) encodes String to byte array using given charset
byte[] getBytes(String charsetName) encodes String into byte array using the named charset

import java.util.Arrays;
/*  ja va 2 s  .  c  o  m*/
public class Main {
  public static void main(String[] argv) {
    String str = "     d e m o 2 s.com    ";
    byte[] bytes = str.getBytes();
    System.out.println(Arrays.toString(bytes));
  }
}