Differences in memory overflow and memory leaks in Java

Although in Java we do not care about the release of memory, the garbage collection mechanism helps us to reclaim unwanted objects, but in fact improper operations can also produce memory problems: memory overflow, memory leaks

Memory overflow: Out of memory: a simple, easy-to-read understanding is that it is not enough.

Memory leaks: Leak of Memory: an object allocates RAM and is not released in time at the end of use, resulting in memory being consumed, not cleaned up in time, and the actual available memory is reduced, as if memory leaks.

For example, improper use of the substring () method in Jdk6 is prone to memory leaks, JDK7 does not have to consider

JDK6 substring Source: Uses the same char array as the parent string value

Public String substring (int beginindex, int endIndex) {
if (Beginindex < 0) {
throw new Stringindexoutofboundsexception (Beginindex);
}
if (EndIndex > Count) {
throw new Stringindexoutofboundsexception (EndIndex);
}
if (Beginindex > EndIndex) {
throw new Stringindexoutofboundsexception (Endindex-beginindex);
}
Return ((Beginindex = = 0) && (endIndex = = count))? this:
New String (offset + beginindex, endindex-beginindex, value);

JDK7 substring Source: You can see that the last creation of a new char array

Public String substring (int beginindex, int endIndex) {
if (Beginindex < 0) {
throw new Stringindexoutofboundsexception (Beginindex);
}
if (EndIndex > Value.length) {
throw new Stringindexoutofboundsexception (EndIndex);
}
int sublen = Endindex-beginindex;
if (Sublen < 0) {
throw new Stringindexoutofboundsexception (Sublen);
}
Return ((Beginindex = = 0) && (endIndex = = value.length))? This
: New String (Value, Beginindex, Sublen);
}

Differences in memory overflow and memory leaks in Java