7.2 String
In java, string is basically an object that represents sequence of char values. The Java platform provides the String class to create and manipulate strings.
Creating Strings:
1) The most direct way to create a string is to write:
String str1 = “Hello Java!”;
2) Using another String object
String str2 = new String(str1);
3) Using new Keyword
String str3 = new String(“Java”);
4) Using + operator (Concatenation)
String str4 = str1 + str2;
or,
String str5 = “hello”+”Java”;
String Length:
length() method returns the number of characters contained in the string object.
String str1 = “Hello Java”;
int len = str1.length();
System.out.println( “String Length is : ” + len );
Concatenating Strings:
The String class includes a method for concatenating two strings:
string1.concat(string2);
This returns a new string that is string1 with string2 added to it at the end. You can also use the concat() method with string literals, as in:
“Hello “.concat(“Java”);
Strings are more commonly concatenated with the + operator, as in:
“Hello ” + ” Java” + “!”
which results in:
“Hello Java!”
String Methods :
1 char charAt(int index)
returns char value for the particular index
2 int length()
returns string length
3 static String format(String format, Object… args)
returns formatted string
4 static String format(Locale l, String format, Object… args)
returns formatted string with given locale
5 String substring(int beginIndex)
returns substring for given begin index
6 String substring(int beginIndex, int endIndex)
returns substring for given begin index and end index
7 boolean contains(CharSequence s)
returns true or false after matching the sequence of char value
8 static String join(CharSequence delimiter, CharSequence… elements)
returns a joined string
9 static String join(CharSequence delimiter, Iterable elements)
returns a joined string
10 boolean equals(Object another)
checks the equality of string with object
11 boolean isEmpty()
checks if string is empty
12 String concat(String str)
concatinates specified string
13 String replace(char old, char new)
replaces all occurrences of specified char value
14 String replace(CharSequence old, CharSequence new)
replaces all occurrences of specified CharSequence
15 String trim()
returns trimmed string omitting leading and trailing spaces
16 String split(String regex)
returns splitted string matching regex
17 String split(String regex, int limit)
returns splitted string matching regex and limit
18 String intern()
returns interned string
19 int indexOf(int ch)
returns specified char value index
20 int indexOf(int ch, int fromIndex)
returns specified char value index starting with given index
21 int indexOf(String substring)
returns specified substring index
22 int indexOf(String substring, int fromIndex)
returns specified substring index starting with given index
23 String toLowerCase()
returns string in lowercase.
24 String toLowerCase(Locale l)
returns string in lowercase using specified locale.
25 String toUpperCase()
returns string in uppercase.
26 String toUpperCase(Locale l)
returns string in uppercase using specified locale.
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