Datentyp String

In der Programmierung ist eine Zeichenkette ein Datentyp, der eine Kette von Zeichen mit fester oder variabler Länge enthält. Damit werden hauptsächlich Wörter, Sätze und ganze Texte gespeichert.

Zeichenketten in Java sind Objekte der Klasse String (java.lang.String). Sie sind nach dem Erzeugen nicht mehr änderbar. Das bedeutet, dass eine Änderung eines String-Inhalts dadurch erreicht wird, dass ein neuer String aus den benötigten Teilen des alten Strings zusammengestellt wird und danach der alte String freigegeben wird. Die erste Zeichenposition im String it 0.

Quellen

Methoden von Java-Strings

Type Method Description  
char charAt (int index) Returns the char value at the specified index.  
int codePointAt (int index) Returns the character (Unicode code point) at the specified index.  
int codePointBefore (int index) Returns the character (Unicode code point) before the specified index.  
int codePointCount (int beginIndex, int endIndex) Returns the number of Unicode code points in the specified text range of this String.  
int compareTo (String anotherString) Compares two strings lexicographically.  
int compareToIgnoreCase (String str) Compares two strings lexicographically, ignoring case differences.  
String concat (String str) Concatenates the specified string to the end of this string.  
boolean contains (CharSequence s) Returns true if and only if this string contains the specified sequence of char values.  
boolean contentEquals (CharSequence cs) Compares this string to the specified CharSequence.  
boolean contentEquals (StringBuffer sb) Compares this string to the specified StringBuffer.  
static String copyValueOf (char[] data) Equivalent to valueOf(char[]).  
static String copyValueOf (char[] data, int offset, int count) Equivalent to valueOf(char[], int, int).  
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 (Locale l, String format, Object… args) Returns a formatted string using the specified locale, format string, and arguments.  
static String format (String format, Object… args) Returns a formatted string using the specified format string and 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.  
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 getBytes (int srcBegin, int srcEnd, byte[] dst, int dstBegin) Deprecated.  This method does not properly convert characters into bytes. As of JDK 1.1, the preferred way to do this is via the getBytes() method, which uses the platform’s default charset.
byte[] getBytes (String charsetName) Encodes this String into a sequence of bytes using the named 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.  
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 isEmpty () Returns true if, and only if, length() is 0.  
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.  
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.  
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 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 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.  
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!) is itself returned.  
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.  
String trim () Returns a string whose value is this string, with any leading and trailing whitespace removed.  
String valueOf (boolean b) Returns the string representation of the boolean argument.  
String valueOf (char c) Returns the string representation of the char argument.  
String valueOf (char[] data) Returns the string representation of the char array argument.  
String valueOf (char[] data, int offset, int count) Returns the string representation of a specific subarray of the char array argument.  
String valueOf (double d) Returns the string representation of the double argument.  
String valueOf (float f) Returns the string representation of the float argument.  
String valueOf (int i) Returns the string representation of the int argument.  
String valueOf (long l) Returns the string representation of the long argument.  
String valueOf (Object obj) | Returns the string representation of the Object` argument.