| static String | copyValueOf(char[] data, int offset, int count) | Equivalent to valueOf(char[], int, int). |
| Optional<String> | describeConstable() | Returns an Optional containing the nominal descriptor for this instance, which is the instance itself. |
| boolean | endsWith(String suffix) | Tests if this string ends with the specified suffix. |
| boolean | equals(Object anObject) | Compares this string to the specified object. |
| boolean | equalsIgnoreCase(String anotherString) | Compares this String to another String, ignoring case considerations. |
| static String | format(String format, Object... args) | Returns a formatted string using the specified format string and arguments. |
| static String | format(Locale l, String format, Object... args) | Returns a formatted string using the specified locale, format string, and arguments. |
| String | formatted(Object... args) | Formats using this string as the format string, and the supplied arguments. |
| byte[] | getBytes() | Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array. |
| void | getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin) | Deprecated. This method does not properly convert characters into bytes. |
| byte[] | getBytes(String charsetName) | Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array. |
| byte[] | getBytes(Charset charset) | Encodes this String into a sequence of bytes using the given charset, storing the result into a new byte array. |
| void | getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin) | Copies characters from this string into the destination character array. |
| int | hashCode() | Returns a hash code for this string. |
| String | indent(int n) | Adjusts the indentation of each line of this string based on the value of n, and normalizes line termination characters. |
| int | indexOf(int ch) | Returns the index within this string of the first occurrence of the specified character. |
| int | indexOf(int ch, int fromIndex) | Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index. |
| int | indexOf(String str) | Returns the index within this string of the first occurrence of the specified substring. |
| int | indexOf(String str, int fromIndex) | Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. |
| String | intern() | Returns a canonical representation for the string object. |
| boolean | isBlank() | Returns true if the string is empty or contains only white space codepoints, otherwise false. |
| boolean | isEmpty() | Returns true if, and only if, length() is 0. |
| static String | join(CharSequence delimiter, CharSequence... elements) | Returns a new String composed of copies of the CharSequence elements joined together with a copy of the specified delimiter. |
| static String | join(CharSequence delimiter, Iterable<? extends CharSequence> elements) | Returns a new String composed of copies of the CharSequence elements joined together with a copy of the specified delimiter. |
| int | lastIndexOf(int ch) | Returns the index within this string of the last occurrence of the specified character. |
| int | lastIndexOf(int ch, int fromIndex) | Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index. |
| int | lastIndexOf(String str) | Returns the index within this string of the last occurrence of the specified substring. |
| int | lastIndexOf(String str, int fromIndex) | Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index. |
| int | length() | Returns the length of this string. |
| Stream<String> | lines() | Returns a stream of lines extracted from this string, separated by line terminators. |
| boolean | matches(String regex) | Tells whether or not this string matches the given regular expression. |
| int | offsetByCodePoints(int index, int codePointOffset) | Returns the index within this String that is offset from the given index by codePointOffset code points. |
| boolean | regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len) | Tests if two string regions are equal. |
| boolean | regionMatches(int toffset, String other, int ooffset, int len) | Tests if two string regions are equal. |
| String | repeat(int count) | Returns a string whose value is the concatenation of this string repeated count times. |
| String | replace(char oldChar, char newChar) | Returns a string resulting from replacing all occurrences of oldChar in this string with newChar. |
| String | replace(CharSequence target, CharSequence replacement) | Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. |
| String | replaceAll(String regex, String replacement) | Replaces each substring of this string that matches the given regular expression with the given replacement. |
| String | replaceFirst(String regex, String replacement) | Replaces the first substring of this string that matches the given regular expression with the given replacement. |
| String | resolveConstantDesc(MethodHandles.Lookup lookup) | Resolves this instance as a ConstantDesc, the result of which is the instance itself. |
| String[] | split(String regex) | Splits this string around matches of the given regular expression. |
| String[] | split(String regex, int limit) | Splits this string around matches of the given regular expression. |
| boolean | startsWith(String prefix) | Tests if this string starts with the specified prefix. |
| boolean | startsWith(String prefix, int toffset) | Tests if the substring of this string beginning at the specified index starts with the specified prefix. |
| String | strip() | Returns a string whose value is this string, with all leading and trailing white space removed. |
| String | stripIndent() | Returns a string whose value is this string, with incidental white space removed from the beginning and end of every line. |
| String | stripLeading() | Returns a string whose value is this string, with all leading white space removed. |
| String | stripTrailing() | Returns a string whose value is this string, with all trailing white space removed. |
| CharSequence | subSequence(int beginIndex, int endIndex) | Returns a character sequence that is a subsequence of this sequence. |
| String | substring(int beginIndex) | Returns a string that is a substring of this string. |
| String | substring(int beginIndex, int endIndex) | Returns a string that is a substring of this string. |
| char[] | toCharArray() | Converts this string to a new character array. |
| String | toLowerCase() | Converts all of the characters in this String to lower case using the rules of the default locale. |
| String | toLowerCase(Locale locale) | Converts all of the characters in this String to lower case using the rules of the given Locale. |
| String | toString() | This object (which is already a string!) |
| String | toUpperCase() | Converts all of the characters in this String to upper case using the rules of the default locale. |
| String | toUpperCase(Locale locale) | Converts all of the characters in this String to upper case using the rules of the given Locale. |
| <R> R | transform(Function<? super String,? extends R> f) | This method allows the application of a function to this string. |
| String | translateEscapes() | Returns a string whose value is this string, with escape sequences translated as if in a string literal. |
| String | trim() | Returns a string whose value is this string, with all leading and trailing space removed, where space is defined as any character whose codepoint is less than or equal to 'U+0020' (the space character). |
| static String | valueOf(boolean b) | Returns the string representation of the boolean argument. |
| static String | valueOf(char c) | Returns the string representation of the char argument. |
| static String | valueOf(char[] data) | Returns the string representation of the char array argument. |
| static String | valueOf(char[] data, int offset, int count) | Returns the string representation of a specific subarray of the char array argument. |
| static String | valueOf(double d) | Returns the string representation of the double argument. |
| static String | valueOf(float f) | Returns the string representation of the float argument. |
| static String | valueOf(int i) | Returns the string representation of the int argument. |
| static String | valueOf(long l) | Returns the string representation of the long argument. |
| static String | valueOf(Object obj) | Returns the string representation of the Object argument. |
</details>
</br>
```java
nombre = nombre.toUpperCase();
System.out.println("Mayúsculas : "+nombre);
nombre = nombre.toLowerCase();
System.out.println("Minúsculas : "+nombre);
int indice = nombre.indexIf('F');
System.out.println("Indice encontrado: "+indice);
char letra = nombre.chartAt(indice);
System.out.println("Caracter en indice(%s) encontrado: %c", indice, letra);
```
#### Formato de Strings
| Format Specifier | Data Type | Output or Return value |
| - | - | - |
| %a | floating point | Returns a Hex output of floating point number |
| %b | Any type | True or False |
| %c | character | Unicode character |
| %d | integer | Decimal Integer |
| %e | floating point | a decimal number in scientific notation |
| %f | floating point | decimal number |
| %g | floating point | decimal number, possibly in scientific notation depending on the precision and value |
| %h | Any type | Hex String of value from hashCode() method |
| %n | None | Platform-specific line separator |
| %o |integer | Octal number |
| %s | Any type | String value |
| %t | Date/Time | %t is the prefix for Date/Time conversions |
| %x | integer | Hex string |
### StringBuilder
```java
String texto = "Ayuda";
texto = texto.concat("-");
texto = texto.concat("me ");
texto = texto.concat("subí ");
texto = texto.concat("al ");
texto = texto.concat("bus ");
texto = texto.concat("equivocado ");
System.out.println(texto);
```
Esto no es bueno pensando en el rendimiento. Para esto existe la clase
**StringBuilder** que ayuda a concatenar Strings de manera más eficiente.
```java
StringBuilder builder = new StringBuilder("Ayuda");
builder.append("-");
builder.append("me ");
builder.append("subí ");
builder.append("al ");
builder.append("bus ");
builder.append("equivocado ");
String texto = builder.toString();
System.out.println(texto);
```
**StringBuilder** es una clase común. Se utiliza new para crear el objeto,
mutable, (usa la misma referencia, sin nuevas asignaciones). E implementa
la interfaz **CharSequence**. Es decir, algunos métodos de la clase **String**
con comunes con **StringBuilder**.
### System
> **Note** Métodos staticos son accesibles sin requerir una instancia
### Object
Clase principal de java, todos los objetos heredan de Object
