Java Strings Class

Strings, which are extensively adopted in Java programming, are a succession of characters. In the Java programming language, strings are extravagances as objects.

The Java platform applies the String class to make and influence strings.

Creating Strings

The most direct way to create a string is to write

String greeting = "Hello world!";

Whenever it meets a string literal in your code, the compiler creates a String object with its value in this case, "Hello world!'.

As with any supplementary object, you can form String objects with the new keyword and a constructor. The String class has 11 constructors that permit you to offer the first value of the string via dissimilar sources, such as a collection of characters.

Example

public class StringDemo {

   public static void main(String args[]) {
      char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.' };
      String helloString = new String(helloArray);  
      System.out.println( helloString );
   }
}

This will produce the following result −

Output

hello.

Note: The String class is immutable; so that one time it is generated a String object never be changed. If there is a requirement to construct many adjustments to Strings of characters, then you should utilize String Buffer & String Builder Classes.

String Length

Methods employed to get information concerning an object are identified as accessor techniques. One accessory technique that you know how to use with strings is the length() technique, which goes back the number of characters holds in the string object.

The following program is an example of length(), method String class.

Example

public class StringDemo {

   public static void main(String args[]) {
      String palindrome = "Dot saw I was Tod";
      int len = palindrome.length();
      System.out.println( "String Length is : " + len );
   }
}

This will produce the following result:

Output

String Length is : 17

Concatenating Strings

The String class includes a method for concatenating two strings

string1.concat(string2);

This returns a new string that is string1 with string2 added to it at the end. You can also use the concat() method with string literals, as in:

"My name is ".concat("Zara");

Strings are more commonly concatenated with the + operator, as in:

"Hello," + " world" + "!"

which results in −

"Hello, world!"

Let us look at the following example −

Example

public class StringDemo {

   public static void main(String args[]) {
      String string1 = "saw I was ";
      System.out.println("Dot " + string1 + "Tod");
   }
}

This will produce the following result −

Output

Dot saw I was Tod

Creating Format Strings

You include printf() and format() schemes to print production with formatted numbers. The String class has an alike class way, format(), that returns a String object rather than a PrintStream object.

Using String's static format() process authorizes you to generate a formatted string that you can reuse, as resisted to a one-time print statement. For example, instead of −

Example

System.out.printf("The value of the float variable is " +
                  "%f, while the value of the integer " +
                  "variable is %d, and the string " +
                  "is %s", floatVar, intVar, stringVar);

You can write:

String fs;
fs = String.format("The value of the float variable is " +
                   "%f, while the value of the integer " +
                   "variable is %d, and the string " +
                   "is %s", floatVar, intVar, stringVar);
System.out.println(fs);

String Methods

Here is the list of methods supported by the String class −

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