String, StringBuilder, StringBuffer

String str = new String("abc");

Creates two object on in the pool and other in heap

an it refers to the heap object

String str1 = "abc";

Creates single object tin the pool

 

Problem -1

String str = new String("abc"); String str1 = "abc"; String str2 ="abc"; String str3 = new String("abc").intern(); System.out.println(str==str1); System.out.println(str.equals(str1)); System.out.println(str1==str2); System.out.println(str1==str3);

Output-

false

true

true

true

we can use the String in Switch case after Java-7

Problem -2

String test = "i want to-test my function";

System.out.println(test.length());

System.out.println(test.charAt(5));

//System.out.println(test.charAt(100)); //Error out of index

System.out.println(test.substring(3, 9)); //9 is excluded

Output

25 t ant to

Problem -3

         String s = "ada";
StringBuilder sb = new StringBuilder("ada");
//System.out.println(s==sb);  // Compiler Error incompatible type
System.out.println(s.equals(sb)); //false
System.out.println(sb.equals(s)); //false


Problem -4
         ArrayList<String> al = new ArrayList<String>();
al.add("a");
al.add("b");
Collections.sort(al);
System.out.println(al);

ArrayList<StringBuilder> alb = new ArrayList<StringBuilder>();
alb.add(new StringBuilder("a") );
alb.add(new StringBuilder("b"));

//Collections.sort(alb); //compiler Error
System.out.println(alb);

StringBuilder and StringBuffer does not implements comparable

	String	StringBuffer	StringBuilder
Storage Area	Constant String Pool	Heap	Heap
Modifiable	No (immutable)	Yes( mutable )	Yes( mutable )
Thread Safe	Yes Every immutable object in Java is thread safe.	Yes All method synchronized.	No
Performance	Fast	Very slow All method synchronized.	Fast