Special String Operations

• These operations include the automatic creation of new String instances from string literals,concatenation of multiple String objects by use of the+operator, and the conversion of other data types to a string representation.

• String Literals

• For each String literal in a program java creates a String object which is enclosed with a double quotes.

// Construct one String from another.
public class StringOperations
{
 public static void main(String args[]) 
 {  
  String s1= "Hello";
  int length = "welcome".length();


   System.out.println("String literals examples");
   System.out.println("String s1 is::"+s1);
   System.out.println("length of string literal //welcome// is::"+length);
 }
}

Output:

String literals examples
String s1 is::Hello
length of string literal //welcome// is::7

• String Concatenation

• We can use only one operator on Strings which is + to concatenate two or more strings .

• It is useful when we want to concatenate a long string by separating into pieces.

// Using concatenation to prevent long lines.
public class ConCat
{
 public static void main(String args[]) {
 String longStr = "This could have been " +
 "a very long line that would have " +
 "wrapped around. But string concatenation " +
 "prevents this.";
 System.out.println(longStr);
 }
}

Output:

This could have been a very long line that would have wrapped around. But string concatenation prevents this.

• String Concatenation with Other Data Types

• We can concatenate a String with other data types using + operator same as Strings

// Using concatenation with other data types.
public class ConCat1
{
 public static void main(String args[]) 
 {
   int date=31;
 String str="Today date is::"+date;  //herer date is an integer value
   System.out.println("concatanating int variable::"+str);

   String str1="Five "+5;    //direct concatenation of int value
   System.out.println("direct concatenation of int value::"+str1);

   String str2= "Five "+2+3;  //when adding two integer values
   System.out.println("when adding two integer values::"+str2);

   String str3 = "Five "+(2+3); //to perform addition
      System.out.println("To perform addition::"+str3);
 }
}

Output:

concatanating int variable::Today date is::31
direct concatenation of int value::Five 5
when adding two integer values::Five 23
To perform addition::Five 5

• String Conversion and toString( )

• The toString( ) method has this general form is:String toString( )

• It simply return a String object that contains the human-readable string that appropriately describes an object of a class.

• We can override this method to execute that when a String is created.

// Override toString() for Box class.
class Box
{
 double width;
 double height;
 double depth;
 Box(double w, double h, double d) 
 {
 width = w;
 height = h;
 depth = d;
 }
 public String toString() 
 {
 return "Dimensions are " + width + " by " +   depth + " by " + height + ".";
 }
}

public class toStringDemo
{
 public static void main(String args[]) 
 {
 Box b = new Box(10, 12, 14);
 String s = "Box b: " + b; // concatenate Box object
 System.out.println(b); // convert Box to string
 System.out.println(s);
 }
}

Output:

Dimensions are 10.0 by 14.0 by 12.0.
Box b: Dimensions are 10.0 by 14.0 by 12.0.