The String class represents strings, and all string literals (such as "abc" ) in Java programs are implemented as instances of this class.
Strings are constants; their value cannot be changed after creation. Because String objects are immutable, they can be safely shared.
public final class String//Source code
implements java.io.Serializable, Comparable<String>, CharSequence
From the definition of the Java.lang.String class, the String class implements the java.io.Serializable (serializable) interface, the Comparable<String> (sortable) interface, and the CharSequence (readable character sequence) interface.
-------------------------------------------------- -ASCII code-----------------------------------------
Familiarity with ASCII is useful when working with characters (mostly numbers and letters)
-------------------------------------------------- -----Common object methods------------------------------------------ ---------
| char charAt(int index) | Returns the char value at the specified index. Example: "Hello".charAt( 0 ) = you Note: If Chinese appears in the code, you need to set the file encoding to ANSI encoding (For example, the settings in notepad++ are: menu bar --> Encoding --> Convert to ANSI encoding) |
| int codePointAt(int index) | Returns the character (Unicode code point) at the specified index. Example: "Hello".codePointAt( 0 ) = 20320 Example: "Programming".codePointAt( 0 ) = 31243 |
| int compareTo(String anotherString) | Compare two strings lexicographically. Example: "Hello".compareTo("Programming") = -10923 -10923 = 20320 - 31243 |
| int compareToIgnoreCase(String str) | Compares two strings lexicographically, regardless of case. 例："Baa".compareToIgnoreCase( "aaa") = 1 |
| String concat(String str) | Concatenates the specified string to the end of this string. ： “Baa” .concat (“aaa”) = “Baaaaa”; |
| boolean contains(CharSequence s) | Returns true if and only if this string contains the specified sequence of char values. 例：“Baa”.contains( "aa" ) = true; |
| boolean endsWith(String suffix) | Tests whether this string ends with the specified suffix. 例："Baa".endsWith( "aa" ) = true; |
| boolean startsWith(String prefix) | Tests whether this string starts with the specified prefix. 例：“Baa”.startsWith( "aa" ) = false; |
| int hashCode() | Returns the hash code for this string. Formula: s[0]*31^(n-1) + s[1]*31^(n-2) + ... + s[n-1] |
| int indexOf(String str) | Returns the index of the first occurrence of the specified string in this string, or -1 if the character does not occur. 例：“Coder666”.indexOf("Coder") = 0; |
| int indexOf(String str, int fromIndex) | Returns the index of the first occurrence of the specified string after the specified index of this string, or -1 if the character does not occur. 例：“Coder666_Coder666”.indexOf("Coder", 3) = 9; |
| intindexOf(char ch) | Returns the index of the first occurrence of the specified string in this string, or -1 if the character does not occur. |
| intindexOf(char ch, int fromIndex) | Returns the index of the first occurrence of the specified string after the specified index of this string, or -1 if the character does not occur |
| int lastIndexOf(int ch) / (String str) | Returns the index of the last occurrence of the specified character (string) in this string. |
| int lastIndexOf(int ch, int fromIndex) | Returns the index of the last occurrence of the specified character before the specified index in this string. |
| int length () | Returns the length of this string. 例：“Coder666”.length() = 8 |
| String replace(char oldChar, char newChar) | Returns a new string obtained by replacing all occurrences of oldChar in this string with newChar. 例：“Coder888”.replace( '8' , '6') = "Coder666"; |
| String replace(CharSequence target, CharSequence replacement) | 返回一个新的字符串，它是通过用 新字符子串replacement 替换此字符串中出现的所有 就字符子串 target 得到的。 例："Coder888_Coder888".replace("888","666") |
| String[] split(String regex) | 根据给定正则表达式的匹配拆分此字符串。 例："Coder888_Coder888".split( "_" ) = { "Coder888" , "Coder666" }; |
| String substring(int beginIndex, int endIndex) | 返回一个新字符串，它是此字符串的一个子字符串。 例：" Coder666_Java".substring( 5 , 8) = "666" |
| char[] toCharArray() | 将此字符串转换为一个新的字符数组。 例：“Coder666”.toCharArray( ) = { ' C ' , ' o ' , ' d ' , ' e ' , ' r ' , ' 6 ' , ' 6 ' , ' 6 '} |
| String toLowerCase() | 将此 String 中的所有字符都转换为小写。 例：“Coder666”.toLowerCase() = "coder666" |
| String toUpperCase() | 使用默认语言环境的规则将此 String 中的所有字符都转换为大写。 例：“Coder666”.toUpperCase() = "CODER666" |
| String trim() | 返回字符串的副本，忽略前导空白和尾部空白。 例：“ Coder666 ”.trim() = "CODER666" |
| boolean matches(String regex) | 告知此字符串是否匹配给定的正则表达式。 |