Learning the Java Language

The Java tutorials were written for the JDK and the practices and practices described on this page do not make use of the improvements introduced in subsequent releases.

A string widely used in Java programming is a series of characters. In the Java programming language, a string is an object.

In this case, "Hello world!" Is a series of string literal strings in the code, enclosed in double quotes. Each time a string literal is found in the code, the compiler creates a String object and its value. In this case, Hello world! is.

Like other objects, you can create a String object with new keywords and constructors. The String class has 13 constructors that allow you to specify initial values ​​for strings using various sources, such as character arrays.

Note: Since the String class is immutable, once created, you can not change the String object. There are several methods in the String class, some of which are described below, but these seem to change the string. As strings are immutable, what these methods actually do is to create and return a new string containing the result of the operation.

The method used to obtain information about an object is called an accessor method. One accessor method that you can use in a string is the length () method, which returns the number of characters in the string object. Executing the next two lines of code will cause len to be 17.

Palindrome ignores the distinction between uppercase and lowercase letters, and symmetrically arranges words or sentences with the same spelling before and after. This is a short and inefficient program to reverse the backstring. It calls the String method charAt (i). This method counts from 0 and returns the ith character in the string.

To complete the inversion of a string, the program converts the string to a character array (initially used for looping), converts the array to a second array (used for loop processing) Convert to a string. The String class contains a method getChars () which converts a character string or part of a character string to a character array, so you can replace the first for loop of the above program.

This connection can mix arbitrary objects. For each object that is not a String, convert it to a String by calling the toString () method.

Note: In the Java programming language, it is not allowed for literal strings to span lines of source files, so you must use the + join operator at the end of each line of a multiline string. For example,

Using + concatenation operators to split lines between lines is also very common in print statements.

I have seen the printing of formatted numbers using the printf () and format () methods. The String class has an equivalent class method format () that returns a String object, not a PrintStream object.

Use String 's static format () method to create a reusable format string instead of a one - time print statement. For example,

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