Java String class

String widely used in Java programming in Java objects belonging to the string, Java provides the String class to create and manipulate strings.

Creating strings

The easiest way to create a string as follows:

String greeting = "Hello world!";

Encountered string constants in the code, where the value is "Hello world!", The compiler will use this value to create a String object.

And other objects, you can use keywords and constructors to create String objects.

String class has 11 kinds of construction methods that provide different parameters to the initialization string, such as a character array parameters:

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 );
   }
}

The above examples compiled results are as follows:

hello.

Note: String class is immutable, so once you create a String object that its value can not be changed. If you need to do a lot of modifications to the string, you should choose to use StringBuffer & StringBuilder class .

String length

The method used to obtain information about the object called accessor methods.

An access control method of the String class is the length () method, which returns the number of characters contained object.

After the following code executes, len variable is equal to 14:

public class StringDemo {
    public static void main(String args[]) {
        String site = "www.w3big.com";
        int len = site.length();
        System.out.println( "本教程网址长度 : " + len );
   }
}

The above examples compiled results are as follows:

本教程网址长度 : 14

Connection String

String class provides a way to concatenate two strings:

string1.concat(string2);

Returns string1 string2 string of new connection. You can also use the concat () method to string constants, such as:

"My name is ".concat("w3big");

More common is to use the '+' operator to concatenate strings, such as:

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

The results are as follows:

"Hello, world!"

Here is an example:

public class StringDemo {
    public static void main(String args[]) {     
        String string1 = "本教程网址：";     
        System.out.println("1、" + string1 + "www.w3big.com");  
    }
}

The above examples compiled results are as follows:

1、本教程网址：www.w3big.com

Create a formatted string

We know that the digital output format can use printf () and format () method. String class using the static method format () Returns a String object rather than a PrintStream object.

Static method format String class () can be used to create a formatted string reusable, and not just for a printout. As follows:

System.out.printf("浮点型变量的的值为 " +
                  "%f, 整型变量的值为 " +
                  " %d, 字符串变量的值为 " +
                  "is %s", floatVar, intVar, stringVar);

You can also write

String fs;
fs = String.format("浮点型变量的的值为 " +
                   "%f, 整型变量的值为 " +
                   " %d, 字符串变量的值为 " +
                   " %s", floatVar, intVar, stringVar);
System.out.println(fs);

String Methods

Here is the String class supports methods for more details, see Java String API documentation: