INTERVIEW QUESTIONS J2EE JAVA DETAILS

Question: What is the diff.between JDK 1.4 and JDK 5.0?

Answer: The main difference:
1. Generics are introduced in jdk1.5
2. The concept of Out-boxing and boxing is introduced.

The main difference:
1. Generics are introduced in jdk1.5
2. The concept of Out-boxing and boxing is introduced. Source: CoolInterview.com

The differences are

1.Generics
Allows programmers to specify the types allowed for Collections
Allows the compiler to enforce the type specifications
//Before
List stringList
//In JDK 1.5
List<String> stringList;

2.Enhanced for loop
A new language constuct for the Iterator pattern
//Before
for(Iterator i = line.iterator();i.hasNext(); )
{
String word = (String)i.next();
…
}
//In JDK 1.5
for(String word: line)
{
…
}

3.Autoboxing
Essentially bridges between the “primitive” types (such as int, boolean) and the
“boxed” types (such as Integer, Boolean)
…
int primitive = 5;
Integer boxed = primitive;
int unboxed = boxed + 5;
…

4.Varargs
Allow a variable number of arguments for methods like printf() or Method.invoke()
Internally parameters are an array of Object
Compiler constructs array for the call
void printf(String format, Object…args);
…
printf(“{0} {1} ”, “Hello”, “World”);
printf(“PI = {0}”, 3.14159);
Source: CoolInterview.com

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