String in java

1. There are 3 classes that can be used to create string in java

- String - StringBuffer - StringBuilder

2. String in java is an Object of java.lang.String

String Class (java.lang.String)

1. String is immutable hence cannot be changed changing a String value creates a new object because if not so then changing a string

would change it for all the literals referring to the string.

Concatenating string to a string does not change the value of the string.

We can assign the string to the concatenated string.

2. String acts like a pool to which String type object refer to.

Example - String a ="Apple";

String b ="Apple";

Does not create two String object since "Apple" was already in memory b simply refers to "Apple" without creating new object.

3. String created through new keyword creates a new String in the memory.

Comparing String

1. equals() or equalsIgnoreCase compares the value of the string.

2. == operator compares the reference of the string.

3. compareTo() return 0,1,-1 if the string are equal,greater or smaller lexicographically.

Substring of a String

public String substring(int startIndex)

public String substring(int startIndex, int endIndex)

startIndex is inclusive

endIndex is exclusive

String methods()

1. toUpperCase()

2. length()

3. trim()

4. valueOf()

5. replace()

6. intern()

StringBuffer class (mutable,thread-safe)

1. insert(int,String)

2. append(String)

3. replace(int,int,String)

4. delete()

5. reverse()

6. capacity()

7. charAt()

8. length()

9. substring()

StringBuilder class (mutable,non-synchronized)

methods same as StringBuffer