6.Newfeatures of Java

8/12/2019 6.Newfeatures of Java

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For each loop

The for-each style of for is an enhanced for loop.

The general form of the for-each version of the for is shown here

for(type itr-var : collection) statement-block

Here, type specifies the type and itr-var specifies the name of an

iteration variable that will receive the elements from a

collection, one at a time, from beginning to end.

It can be used for iterating multidimensional arrays.


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Here is an entire program that demonstrates the for-each version of the

for just described:

// Use a for-each style for loop.

class ForEach {

public static void main(String args[]) {

int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

int sum = 0;

for(int x : nums) {

System.out.println("Value is: " + x);sum += x;

}

System.out.println("Summation: " + sum);

}

}


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In cases where the maximum number of potential arguments was larger, or

unknowable,a second approach was used in which the arguments were put into a

array, and then the array was passed to the method. This approach is illustrated b

the following program:

class PassArray {

static void vaTest(int v[]) {

System.out.print("Number of args: " + v.length +" Contents: ");

for(int x : v)

System.out.print(x + " ");

System.out.println();

}

public static void main(String args[])

{ int n1[] = { 10 };//variable length arguments

int n2[] = { 1, 2, 3 };

vaTest(n1);

vaTest(n2); } }


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Variable Length Arguments

Sometimes we need creation of methods That take a variable num

of arguments. This feature is called varargsand it is short forvariable-length arguments. A method that takes a variable numb

arguments is called a variable-arity method, or simply a varargs

method.

Situations that require that a variable number of arguments be pas

to a method are not unusual.For example, a method that opens an Internet connection might ta

user name, password, filename, protocol, and so on, but supply

defaults if some of this information is not provided. In this situa

it would be convenient to pass only the arguments to which the

defaults did not apply.


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The varargs uses ellipsis i.e. three dots after the data type. Syntax is as follow

return_type method_name(data_type... variableName){}

EX:

classVarargsExample1{staticvoiddisplay(String... values){

System.out.println("display method invoked ");

for(String s:values){

System.out.println(s);

}

publicstaticvoidmain(String args[]){

display();//zero argument

display("my","name","is","varargs");//four arguments

}

}


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Rules:While using the varargs, you must follow some rules otherwise progracode won't compile. The rules are as follows:

There can be only one variable argument in the method. Variable argument (varargs) must be the last argument.

EX:

classVarargsExample3{

staticvoiddisplay(intnum, String... values){

System.out.println("number is "+num);for(String s:values){

System.out.println(s);

}

}


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Static import The static import feature of Java 5 facilitate the java programmer to access any st

member of a class directly. There is no need to qualify it by the class name.

Adv: Less coding is required if you have access any static member of a class often

Disadv: If you overuse the static import feature, it makes the program unreadable

unmaintainable.

Example:

importstaticjava.lang.System.*;

classStaticImportExample{publicstaticvoidmain(String args[]){

out.println("Hello");//Now no need of System.out

out.println("Java");

}

}


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Thank You

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6.Newfeatures of Java