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PermGen elimination in JDK 8
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Fixed size at startup – difficult to tune.
Internal Hotspot types were Java objects : Could move with full GC, opaque, not strongly typed and hard to debug, needed meta-metadata.
Simplify full collections : Special iterators for metadata for each collector
Want to deallocate class data concurren...
String.format() to format double in java
...alFormat.setRoundingMode(RoundingMode.UP);
Here are the imports:
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;
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Can overridden methods differ in return type?
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Java supports* covariant return types for overridden methods. This means an overridden method may have a more specific return type. That is, as long as the new return type is assignable to the return type of the method you ar...
What's the best way to check if a String represents an integer in Java?
... (c < '0' || c > '9')... are the <= and >= operators faster in Java?
– Anonymous
Oct 26 '08 at 1:43
3
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Should I use Java's String.format() if performance is important?
...d + comes ahead of format. by a factor of 5 to 6.
Try it your self
import java.io.*;
import java.util.Date;
public class StringTest{
public static void main( String[] args ){
int i = 0;
long prev_time = System.currentTimeMillis();
long time;
for( i = 0; i< 100000; i++){
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Java optional parameters
How do I use optional parameters in Java? What specification supports optional parameters?
17 Answers
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Does Java casting introduce overhead? Why?
... casting is not feasible, JVM must throw a ClassCastException.
Taken from JavaWorld: The cost of casting
Casting is used to convert between
types -- between reference types in
particular, for the type of casting
operation in which we're interested
here.
Upcast operations (also cal...
Comparing boxed Long values 127 and 128
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TL;DR
Java caches boxed Integer instances from -128 to 127. Since you are using == to compare objects references instead of values, only cached objects will match. Either work with long unboxed primitive values or use .equals() to ...
Java: Class.this
I have a Java program that looks like this.
5 Answers
5
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Java 8 method references: provide a Supplier capable of supplying a parameterized result
...ise you will get an error message like MyException cannot be converted to java.lang.RuntimeException
Update:- This was an issue with an older version of JDK. I don't see this issue with the latest versions.
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