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A heap error will be generated if the heap is continued to be accessed even if there is no memory left in the heap.
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public class ShowHeapError {
Vector<String> names = new Vector<String>();
String newName=null;
InputStreamReader input = new InputStreamReader(System.in);
BufferedReader reader = new BufferedReader(input);
public void addNames(){
do{
//adding unknown number of records to a list
//the user can enter as much data as he wants and exhaust the heap
System.out.print(" To quit, enter \"quit\"\nEnter record: ");
try {
newName = reader.readLine();
if(!newName.equalsIgnoreCase("quit")){
//names are continued to be added without bothering about the size on the heap
names.addElement(newName);
}
} catch (IOException e) {
}
System.out.println(newName);
}
while (!newName.equalsIgnoreCase("quit"));
}
public static void main(String[] args) {
ShowHeapError demo = new ShowHeapError();
demo.addNames();
}
}
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maximum heap size: Smaller of 1/4th of the physical memory or 1GB
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 publicpublic class ShowHeapError { /*assuming the heap size as 512mB (calculated as 1/4th of 2 GB RAM = 512mB) * Considering long values being entered (64 bits each, the max number of elements * would be 5122mB/64bits = 67108864) */ Vector<Long> names = new Vector<Long>(67108865); long newID=0L; int count = 67108865; int i = 0; InputStreamReader input = new InputStreamReader(System.in); Scanner reader = new Scanner(input); public void addNames(){ do{ /*adding unknown number of records to a list * the user can enter more number of IDs than what the heap can support and exhaust the heap * assume that the record ID is a 64 bit long value */ System.out.print(" To quit, enter -1\nEnter recordID: "); newID = reader.nextLong(); //names are continued to be added without bothering about the size on the heap names.addElement(newID); System.out.println(newID); i++; }while (i<count || newID!=-1); } public static void main(String[] args) { ShowHeapError demo = new ShowHeapError(); demo.addNames(); } } |
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