Java.lang.Appendable

It is a public abstract interface. Many classes and interfaces are extending this abstract interface for different purposes.


SuperClass of Appendable:-

From java.lang package -

StringBuffer

StringBuilder

From java.io package -

BufferedWriter

CharArrayWriter

FileWriter

FilterWriter

OutputStreamWriter

PipedWriter

PrintStream

PrintWriter

StringWriter

Writer

From java.nio package - 

CharBuffer

From java.rmi.server package -

LogStream

All the above classes and interfaces are designed for different purposes and used all abstract method defined in the AbstractStringBuilder class for their own way of implementing the code by overriding these four methods.  

Methods of AbstractStringBuilder class

public abstract Appendable append(CharSequence cs) throws IOException;

public abstract Appendable append(CharSequence cs, int i, int j)  throws IOException;

public abstract Appendable append(char cs) throws IOException;

Read More

java.lang.AbstractStringBuilder

It is a private class or more specifically we can say its a ' private - package ' class i.e it is declared as not public and as abstract. As it was not there before the release of JDK 1.5 and was first introduced in java 5.0 as the superclass for both StringBuffer and StringBuilder.  Initially before JDK 1.5 there was only one class i.e StringBuffer ( which is thread safe ) and was extending Object class, but later with the release of JDK 1.5 AbstractStringBuilder and StringBuilder was introduced and now StringBuffer is extending AbstractStringBuilder . 

What is private - package class ?

If we declare a non-public class in a package whose scope will be within that package only , in other terms we create any instance of the class outside the package and hence can be considered as private class and called as private-package class. 

Aim behind intoducing AbstractStringBuilder ?

As we knowing that there are two identical class i.e StringBuilder and StringBuffer expects StringBuffer is thread safe and where as StringBuilder is not. Thus all the methods and their implementation are almost identical so instead of writing two times for both the classes they introduce a non-public abstract class i.e AbstractStringBuilder class which has same method with implementation and hence both are classes are using its implementation. 

Interesting facts of AbstractStringBuilder 

If we notice in AbstractStringBuilder class many method returns its own class instance only and its sub-classes i,e StringBuffer and StringBuilder both the classes override the methods of AbstractStringBuilder class and restrict the return type to their own class instance, this narrowing the return type by overiding the method in its sub-class is termed as ' co-variant return ', which is seen with the release of JDK 1.5 and with the later versions.    

Constrcutors of AbstractStringBuilder class

  AbstractStringBuilder()

  AbstractStringBuilder(int i)

Instance variables of AbstractStringBuilder class

1. char[]   value;
2. int        count;
3. static final int[]    sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999, 99999999, 999999999, 2147483647 };

Methods of AbstractStringBuilder class

  public int length()

  

  public int capacity()

  public void ensureCapacity(int i)

  void expandCapacity(int i)

  public void trimToSize()

  public void setLength(int i)

  public char charAt(int i)

  public int codePointAt(int i)

  public int codePointBefore(int i)

  public int codePointCount(int i, int j)

  public int offsetByCodePoints(int i, int j)

  public void getChars(int i, int j, char[] c, int k)

  public void setCharAt(int i, char c)

  public AbstractStringBuilder append(Object obj)

  public AbstractStringBuilder append(String s)

  public AbstractStringBuilder append(StringBuffer sb)

  public AbstractStringBuilder append(CharSequence cs)

  public AbstractStringBuilder append(CharSequence cs, int i, int j)

  

  public AbstractStringBuilder append(char[] ch)

  

  public AbstractStringBuilder append(char[] ch, int i, int j)

  public AbstractStringBuilder append(boolean b)

  public AbstractStringBuilder append(char c)

  public AbstractStringBuilder append(int i)

  static int stringSizeOfInt(int i)

  public AbstractStringBuilder append(long l)

  static int stringSizeOfLong(long l)

  public AbstractStringBuilder append(float f) 

  public AbstractStringBuilder append(double d)

  public AbstractStringBuilder delete(int i, int j)

  public AbstractStringBuilder appendCodePoint(int i)

  public AbstractStringBuilder deleteCharAt(int i)

  

  public AbstractStringBuilder replace(int i, int j, String s)

  

  public String substring(int i)

  public CharSequence subSequence(int i, int j)

  public String substring(int i, int j)

  public AbstractStringBuilder insert(int i, char[] c, int j, int k)

  

  public AbstractStringBuilder insert(int i, Object o)

  public AbstractStringBuilder insert(int i, String s)

  public AbstractStringBuilder insert(int i, char[] c)

  public AbstractStringBuilder insert(int i, CharSequence cs)

  public AbstractStringBuilder insert(int i, CharSequence cs, int j, int k)

  public AbstractStringBuilder insert(int i, boolean b)

  public AbstractStringBuilder insert(inti, char c)

  public AbstractStringBuilder insert(int i, int j)

  public AbstractStringBuilder insert(int i, long l)

  public AbstractStringBuilder insert(int i, float f)

  public AbstractStringBuilder insert(int i, double d)

  public int indexOf(String s)

  public int indexOf(String s, int i)

  public int lastIndexOf(String s)

  public int lastIndexOf(String s, int i)

  public AbstractStringBuilder reverse()

  public abstract String toString();

  final char[] getValue()

Read More

java.lang.CharSequence

It is the only abstract interface in the java.lang package. It is the basic interface containing non-implemented methods all regarding and involving characters only like length() , charAt() etc and a special method i.e toString() method. It is the super class of many of the classes and interfaces, which are shown below.

Implementation class for the abstract method declared in the in the CharSequence interface are:-

AbstractStringBuilder (c)   of [ java.lang package ]

String (c)                             of [ java.lang package ]

StringBuffer (c)                   of [ java.lang package ]

StringBuilder (c)                 of [ java.lang package ]

CharBuffer (c)                     of [ java.nio package ]

Segment (c)                         of [ javax.swing.text package ]

Note : (c) represent the class. All the above mentioned names are java class.


Methods of the CharSequence interface :

public abstract int length();

public abstract char charAt(int i);

public abstract CharSequence subSequence(int i, int j);

public abstract String toString();


Some of the important points of CharSequence interface :

* It was first introduced with the release of JDK 1.4.
* CharSequence is originally is the sequence of character and which combines to form a String only,
so we can call a string as the CharSequence.

Read More