Term
| Difference between String, StringBuffer and StringBuilder |
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Definition
| String is immutiable, StringBuffer is mutable but thread safe, StringBuilder is thread unsafe. |
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Term
| As Coding convention class name begins with _ case and variable name with _ case |
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Definition
CLass Names begin with uppercase eg: class EmployeesOfLehman {
...
}
variable with lowercase eg:
int noOfEmployees |
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Term
| what is difference between final, finally, and finalize |
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Definition
.final class cannot be extended, final variable cannot be changes, and final method cannot be overridden.
.finally is tha last block in try catch block it is always run regardless.
. finalize is executed when an object garbage collected. |
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Term
| Difference between function overriding vs. function hiding |
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Definition
Class (static) methods with the same signature in both parent and chlid class result in hiding.
Instance methods results in overriding. |
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Term
| what are some of the methods provided by Object class |
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Definition
| HashCode(), finalize(), toString(), equals |
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Term
| How can u obtain number of active java threads from java |
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Definition
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Term
| Why should wait be always called in while loop |
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Definition
| Always invoke wait inside a loop that tests for the condition being waited for. Don't assume that the interrupt was for the particular condition you were waiting for, or that the condition is still true. |
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Term
| what is transient keyword |
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Definition
| a variable declared transient will not be seralized |
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Term
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Definition
| since each thread has it own stack segment local variables are not shared between threads. But if u want to synch the value of a local variable between threads then use volatile. If one thread will update the value all others will get the updated value if the local variable is declared as volatile |
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Term
| In HashMap how would you fine tune, ie reduce collision. |
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Definition
| Fine tuning is done based on load factor. Load factor is defaulted to .75, which means that when hash table is 75% full the increase the size and rehash the table. Also initial capacity could be set so that the first rehashing happens only after a while. |
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Term
| To be able to sort elements in, say, ArrayList the element must implement |
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Definition
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Term
| To be able to insert elements into a HashMap the elements must |
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Definition
| implements methods hashCode() and equals() |
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Term
| difference between equals() method and comparable interfafce |
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Definition
equals() is used with HashCode and compaing object for equality.
Comparable interface is used strictly for sorting purposes. |
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