JUnit + Eclipse + Maven = fun

Given:

/src/test/java/com/helloworld/a.xml with body <src_test_java/>
/src/test/resources/com/helloworld/a.xml with body <src_test_resources/>
/src/main/java/com/helloworld/a.xml with body <src_main_java/>
/src/main/resources/com/helloworld/a.xml with body <src_main_resources/>

Run the following JUnit(NOT under /src/test/java/com/helloworld/) in Eclipse configured by Maven with Eclipse plugin (mvn eclipse:eclipse):

A: this.getClass().getResource("a.xml”);
B: this.getClass().getResource("/com/helloworld/a.xml");
C: this.getClass().getResourceAsStream("a.xml");
D: this.getClass().getResourceAsStream("/com/helloworld/a.xml");
E: this.getClass().getClassLoader().getResource("a.xml");
F: this.getClass().getClassLoader().getResource("/com/helloworld/a.xml");
G: this.getClass().getClassLoader().getResourceAsStream("a.xml");
H: this.getClass().getClassLoader().getResourceAsStream("/com/helloworld/a.xml");

What should the result look like?

Answer:
A: empty string
B: <src_test_resources/>
C: empty string
D: <src_test_resources/>
E: null
F: null
G: null
H: null

java.lang.Long.intValue() or casting long to int

Problem:

public static void main(String args[]) {

Long l = Long.MAX_VALUE;

System.out.println(l.longValue());

System.out.println(l.intValue());

System.out.println("---------------\n");

Long l2 = Long.valueOf(Integer.MAX_VALUE);

System.out.println(l2.longValue());

System.out.println(l2.intValue());

System.out.println("---------------\n");

Long l3 = Long.valueOf(Integer.MAX_VALUE) + 1;

System.out.println(l3.longValue());

System.out.println(l3.intValue());

System.out.println("---------------\n");

Long l4 = Long.valueOf(Integer.MAX_VALUE) + 2;

System.out.println(l4.longValue());

System.out.println(l4.intValue());

System.out.println("---------------\n");

Long l5 = Long.valueOf(Integer.MAX_VALUE) + Integer.MAX_VALUE;

System.out.println(l5.longValue());

System.out.println(l5.intValue());

System.out.println("---------------\n");

Long l6 = Long.valueOf(Integer.MAX_VALUE) + Integer.MAX_VALUE + 1;

System.out.println(l6.longValue());

System.out.println(l6.intValue());

System.out.println("---------------\n");

Long l7 = Long.valueOf(Integer.MAX_VALUE) + Integer.MAX_VALUE + 2;

System.out.println(l7.longValue());

System.out.println(l7.intValue());

System.out.println("---------------\n");

}

9223372036854775807

-1

---------------

2147483647

2147483647

---------------

2147483648

-2147483648

---------------

2147483649

-2147483647

---------------

4294967294

-2

---------------

4294967295

-1

---------------

4294967296

0

---------------

Solution:

use one of the suggested methods mentioned at this thread:

http://stackoverflow.com/questions/1590831/safely-casting-long-to-int-in-java

Use autoboxing/unboxing cautiously

Problem:

public static void main(String args[]) {

Long long1 = Long.valueOf(123L);

Long long2 = new Long("123");

Long long3 = Long.parseLong("123");

long long4 = Long.valueOf(123L);

long long5 = new Long("123");

long long6 = Long.parseLong("123");

System.out.println("long1==long2:"+ (long1==long2));

System.out.println("long1==long3:"+ (long1==long3));

System.out.println("long1==long4:"+ (long1==long4));

System.out.println("long1==long5:"+ (long1==long5));

System.out.println("long1==long6:"+ (long1==long6));

System.out.println("long2==long3:"+ (long2==long3));

System.out.println("long2==long4:"+ (long2==long4));

System.out.println("long2==long5:"+ (long2==long5));

System.out.println("long2==long6:"+ (long2==long6));

System.out.println("long3==long4:"+ (long3==long4));

System.out.println("long3==long5:"+ (long3==long5));

System.out.println("long3==long6:"+ (long3==long6));

System.out.println("long4==long5:"+ (long4==long5));

System.out.println("long4==long6:"+ (long4==long6));

System.out.println("long5==long6:"+ (long5==long6));

}

long1==long2:false
long1==long3:true
long1==long4:true
long1==long5:true
long1==long6:true
long2==long3:false
long2==long4:true
long2==long5:true
long2==long6:true
long3==long4:true
long3==long5:true
long3==long6:true
long4==long5:true
long4==long6:true
long5==long6:true

Solution: If you don't know the origin of the Long object, you may want to check if it is null AND longObject.longValue() for value comparison.

java 5 on mountain lion

http://www.s-seven.net/java_15_mountain_lion

Invoking parent private method by reflection

public class SuperClass {

boolean superField = true;

private void superMethod(boolean superField) {
System.out.println("superMethod() called - param:" + superField);
}
}

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class SubClass extends SuperClass {
public static void main(String args[]) {
SubClass subClassInstance = new SubClass();
try {
Method declaredMethod = SuperClass.class.getDeclaredMethod("superMethod", boolean.class);
declaredMethod.setAccessible(true);

declaredMethod.invoke((SuperClass)subClassInstance, new Object[] {false}); //I remember that there was a situation this explicit cast is required

} catch (NoSuchMethodException e) {
} catch (SecurityException e) {
} catch (IllegalAccessException e) {
} catch (IllegalArgumentException e) {
} catch (InvocationTargetException e) {
}
}
}

JVM HIGH LOAD WITHOUT ANY REASON (JAVA LEAP YEAR BUG)

Yes, I spent the whole day on this, someone saved my life:

http://blog.wpkg.org/2012/07/01/java-leap-second-bug-30-june-1-july-2012-fix/

MapQuest Android MapView vs Google Android MapView

Problem: Cannot align the MapView properly in MapQuest.

Solution: Do your own bit-wise OR!!!

Google Android MapView LayoutParams:

int a = MapView.LayoutParams.BOTTOM_CENTER; //81

int b = MapView.LayoutParams.BOTTOM; //80

int c = MapView.LayoutParams.CENTER_HORIZONTAL; //1

int d = MapView.LayoutParams.BOTTOM | MapView.LayoutParams.CENTER_HORIZONTAL; // 81

it makes sense, doesn't it?

How about MapQuest Android MapView LayoutParams?

int a = MapView.LayoutParams.BOTTOM_CENTER; //35

int b = MapView.LayoutParams.BOTTOM; //32

int c = MapView.LayoutParams.CENTER_HORIZONTAL; //1

int d = MapView.LayoutParams.BOTTOM | MapView.LayoutParams.CENTER_HORIZONTAL; // 33

hmmm...something doesn't seem right here...