Java String Introduction

Strings are very common data types on computers. This page describes the basics of Java strings, chars, +, length (), and substring ().

A Java string is a series of letters grouped, such as the word "Hello" or the phrase "practice make perfect". Create a string in your code by writing characters between double quotes.

This figure shows a string object in memory consisting of individual characters. You can see the meaning of index numbers 0, 1 and 2.

The + (plus) operator between strings combines them to form a new, larger string. The larger string is only the character of the first string that is placed with the character of the second string.

The character string is not composed only of letters a - z. Characters may be punctuation marks or other wrong characters. For example, in the string "hi", the third letter is a space. All of these apply to the string stored in the variable as follows:

The "length" of a character string is the number of characters in it. Therefore, "hi" is the length 2, "Hello" is the length () method of the length string and returns the length as follows.

Characters in the string are identified by the "index" number. In "Hello", the leftmost char (H) is index 0, the next char (e) is index 1, and so on. The index of the last character is always less than the length. In this case, the length is 5, "o" is the index. That is, the characters in the string are at indices 0, 1, 2, ... until the length is 1. In the next section we will slice the string using the subscript number and use substring () to dice.

The substring () method uses the index number to select part of the string and identifies the part of interest. The simplest form substring (int start) takes the starting index number and returns a new string starting at that index and continuing from the end of the string.

The above strsubstring (1) returns "ello" and selects the "Hello" part starting from index 1 ("H" at index 0, "e" at index 1).

Complex strings containing runtime data: Friends, Android let you know. The platform supports parameterized strings in a syntax similar to that used in Java's String.format (). In addition to this, multiple strings are supported (use different numbers based on a certain number of strings). For the official documentation of parameterized strings and multiple strings, see this StackOverflow post. Who is the one who likes to create cumbersome findViewById calls and maintain references to those views in the current namespace? In this case, it is necessary to keep the view ID so that the view ID used in findViewById can be specified. This is because the auto-complete function of Android Studio is recommended each ID (from all of the layout), you can only use the ID that exists in the current layout tree to findViewById. If it does not exist, null is returned (there is a possibility of NullPointerException)

Let's take a quick look at the strings and string declarations learned in Java. A Java string is a string of values ​​(text and / or numbers). The text string holds its value in the program. It is set when you set it. Creating an instance of String creates a new String object, regardless of whether you are using a value in memory or using an existing text string in shared memory. This space in memory is called a constant pool. There are several ways to manipulate strings, regardless of which method is used to declare a string. Use the tool to compare, change, combine, and separate strings.

Today I will talk about strings in Java. If you write Java a lot, you can see that a String is considered to be the first type object, even though the String is not one of the eight basic types. What you might not know is the best way to handle strings in production applications. To do this you need to understand how to internationalize / localize strings, manipulate very large strings, or drill down into string comparison rules. Let's get started ... I will unlock this. Internationalization (internationalization) is the process of providing human-readable strings in various languages. Internationalization (l10n), on the other hand, takes into account geographical and cultural issues. Internationalization is a curriculum and localization is sophisticated. For example, the strings "Choose your favorite color" and "Choose your favorite color" are all in English (i18n), the former is for the US (en-US) and the latter is for the British (en-GB).