Name: tb29552 Date: 10/02/2000


/*
C:\>java -version
java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0-C)
Java HotSpot(TM) Client VM (build 1.3.0-C, mixed mode)

If a thread invokes the substring(int) method on a shared StringBuffer, and
another thread concurrently invokes delete(int, int) or deleteCharAt(int) on the
same StringBuffer, substring may throw a StringOutOfBoundsException. This
happens because substring is not synchronized and may use an old size but a new
buffer.

The following example eventually throws an exception:

% java -showversion SbTest
java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0)
Java HotSpot(TM) Client VM (build 1.3.0, mixed mode)

java.lang.StringIndexOutOfBoundsException: String index out of range: 26
        at java.lang.StringBuffer.substring(StringBuffer.java:702)
        at java.lang.StringBuffer.substring(StringBuffer.java:679)
        at SbTest$2.run(SbTest.java:42)
*/

class SbTest {
    static StringBuffer sb =
        new StringBuffer("abcdefghijklmnopqrstuvwxyz");

    public static void main(String[] args) {
        Thread t1 = new Thread() {
            public void run() {
                while (true) {
                    sb.deleteCharAt(0);
                    sb.insert(0, 'a');
                }
            }
        };
        Thread t2 = new Thread() {
            public void run() {
                while (true) {
                    sb.substring(0);
                }
            }
        };
        t1.start();
        t2.start();
    }
}

(Review ID: 110249)
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