Module# 15: String Class Lecture#58: StringBuffer Class

// Example 58.1 : Creating StringBuffer objects

import java.lang; /

// It is not necessary as it is by default imported in all programs.

class StringBufferDemo {

public static void main(String args[]) {

StringBuffer strOb1 = "First String";

StringBuffer strOb2 = "Second String";

StringBuffer strOb3 = strOb1 + " and " + strOb2;

System.out.println(strOb1);

System.out.println(strOb2);

System.out.println(strOb3);

StringBuffer sb1 = new StringBuffer();

StringBuffer sb2 = new StringBuffer(strOb3);

StringBuffer aString = new StringBuffer(“An example of string is” + sb2);

}

}

// Example 58.2: Modifying strings

public class ModifyStringDemo{

public static void main(String args[]){

StringBuffer text = new StringBuffer("Data Structure ");

text.append(“C++");

System.out.print(text);

text.insert(15,“with ");

System.out.print(text);

text.replace(20,23,"Java");

System.out.print(text);

text.delete(14,19);

}

}

// Example 58.3 : The reversing a string

public class StringReverseDemo{

public static void main(String args[]){

StringBuffer text=new StringBuffer("Data Structure With With Java");

text.reverse();

System.out.print(text);

}

}

// Example 58.3: Merging of strings with String and StringBuffer methods

public class ConcatTest{

public static String concatWithString() {

String s = "Java";

for (int i=0; i<10000; i++){

s = s.concat(“NPTEL“);

}

return s;

}

public static String concatWithStringBuffer(){

StringBuffer sb = new StringBuffer("Java");

for (int i=0; i<10000; i++){

sb.concat(“NPTEL");

}

return sb.toString();

}

// The driver class for the execution of two methods

public static void main(String[] args){

long startTime = System.currentTimeMillis();

concatWithString();

System.out.println("Time taken by Concating with String: “

+(System.currentTimeMillis()-startTime)+"ms");

startTime = System.currentTimeMillis();

concatWithStringBuffer();

System.out.println("Time taken by Concating with StringBuffer: “

+(System.currentTimeMillis()-startTime)+"ms");

}

}

// Example 58.4 : length( ) and capacity( )

// StringBuffer length vs. capacity.

class StringBufferDemo {

public static void main(String args[]) {

StringBuffer sb = new StringBuffer("Hello");

System.out.println("buffer = " + sb);

System.out.println("length = " + sb.length());

System.out.println("capacity = " + sb.capacity());

}

}

// Example 58.5 : charAt( ) and setCharAt( )

class setCharAtDemo {

public static void main(String args[]) {

StringBuffer sb = new StringBuffer("Hello");

System.out.println("buffer before = " + sb);

System.out.println("charAt(1) before = " + sb.charAt(1));

sb.setCharAt(1, 'i');

sb.setLength(2);

System.out.println("buffer after = " + sb);

System.out.println("charAt(1) after = " + sb.charAt(1));

}

}

// Example 58.6 : Hash code of string objects

public class HashCodeTest{

public static void main(String args[]){

System.out.println("Hashcode test of String:");

String str=“Java";

System.out.println(str.hashCode());

str=str+“NPTEL";

System.out.println(str.hashCode());

System.out.println("Hashcode test of StringBuffer:");

StringBuffer sb=new StringBuffer(“Java");

System.out.println(sb.hashCode());

sb.append(“NPTEL");

System.out.println(sb.hashCode());

}

}