String.substring()

This question was mainly asked to see if developer is familiar with risk of memory leak, which substring can create. Until Java 1.7, substring holds reference of original character array, which means even a substring of 5 character long, can prevent 1GB character array from garbage collection, by holding a strong reference. This issue is fixed in Java 1.7, where original character array is not referenced any more, but that change also made creation of substring bit costly in terms of time. Earlier it was on the range of O(1), which could be O(n) in worst case on Java 7.

In <1.7 version, substring() calls constructor:

String(int offset, int count, char value[]) {
	this.value = value;
	this.offset = offset;
	this.count = count;
}

the char[] is the strong reference <<Back