Strings

[prarthana reddy]

public class Test {

public static void main(String args[])
{
String s0 = new String("Java");
String s1 = s0.trim();
String s2 = s0.substring(0, 4);

String s3 = s0.toString();

System.out.println(s0 == s1);
System.out.println(s0 == s2);
System.out.println(s0 == s3);
}
}
In the above code , wont the trim(), substring() return a new string? But the answer is true for all the cases..

[wise owen]

If these functions do not change string then the origanal reference will be return.
For example: public String trim() API:

If this String object represents an empty character sequence, or the first and last characters of character sequence represented by this String object both have codes greater than '\u0020' (the space character), then a reference to this String object is returned.

[ August 15, 2006: Message edited by: wise owen ]

[Simeon Cherniy]

Method trim (source code) . See 1471-1473 line (your case)

1468  public String trim()
1469  {
1470    int limit = count + offset;
1471    if (count == 0 || (value[offset] > '\u0020'
1472                       && value[limit - 1] > '\u0020'))
1473      return this;
1474    int begin = offset;
1475    do
1476      if (begin == limit)
1477        return "";
1478    while (value[begin++] <= '\u0020');
1479    int end = limit;
1480    while (value[--end] <= '\u0020');
1481    return substring(begin - offset - 1, end - offset + 1);
1482  }

And the same for method substring (line 1125-1126):

1121  public String substring(int beginIndex, int endIndex)
1122  {
1123    if (beginIndex < 0 || endIndex > count || beginIndex > endIndex)
1124      throw new StringIndexOutOfBoundsException();
1125    if (beginIndex == 0 && endIndex == count)
1126      return this;
1127    int len = endIndex - beginIndex;
1128    // Package constructor avoids an array copy.
1129    return new String(value, beginIndex + offset, len,
1130                      (len << 2) >= value.length);
1131  }
 

[ August 15, 2006: Message edited by: Simeon Cherniy ]

[prarthana reddy]

Thankyou for your answer..but am not very clear about it

[wise owen]

    
  String s0 = new String("Java "); 
  String s1 = s0.trim(); 
  String s2 = s0.substring(0, 4);
 
  String s3 = s0.toString();
 
  System.out.println(s0 == s1); //false
  System.out.println(s0 == s2); //false
  System.out.println(s0 == s3); //true