StringBuffer object comparision

Question

I have created two StringBuffer as follows

StringBuffer buffer1 = new StringBuffer("Text");
StringBuffer buffer2 = new StringBuffer(buffer1);

If Compare those StringBuffer with equals method then it returned false?

if (buffer1.equals(buffer2))
    System.out.println("true");
else
    System.out.println("false");

equals() compares the content of the string.So, i dont know what is the reason for returning false here...

Please Guide me get out of this issue?

Note: Also consider to use StringBuilder instead of StringBuffer if you don't need it to be thread safe. — Puce
– Puce, Commented Apr 26, 2012 at 10:03
That's because the two buffers are not equal. If you want to compare the equality of the Strings that the two buffers contain, then you will have to use toString() on each buffer, and compare the results. — Jon
– Jon, Commented Apr 26, 2012 at 10:06
buffer1.equals(buffer2) is same thing like buffer1 == buffer2. That's why you have to get String content out to compare. — Benz Bumroungruksa
– Benz Bumroungruksa, Commented Apr 26, 2012 at 10:08

adranale · Accepted Answer · 2012-04-26 10:23:33Z

5

StringBuffer.equals() does NOT compare the string contents. You have to do toString().equals().

edited Apr 26, 2012 at 10:23

answered Apr 26, 2012 at 10:00

adranale

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1 Comment

Puce Over a year ago

toString() not getString(), but else +1

Nagaraju Badaeni · Accepted Answer · 2012-04-26 10:04:54Z

You are comparing objects not text. buffer1 is different form buffer2

read JDK reference of equals method

The equals method implements an equivalence relation on non-null object references:

It is reflexive: for any non-null reference value x, x.equals(x) should return true. It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true. It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true. It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified. For any non-null reference value x, x.equals(null) should return false. The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Sachin Mhetre · Accepted Answer · 2020-07-14 05:16:32Z

3

You should use toString().

if (buffer1.toString()
          .equals(buffer2.toString()))
      System.out.println("true");
else
      System.out.println("false");

edited Jul 14, 2020 at 5:16

answered Apr 26, 2012 at 10:02

Sachin Mhetre

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