Admin: 1 версия

2010-06-01T05:19:03Z

1 версия

в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

Новая страница

== Iterating over Multidimensional Arrays: Use for-each style for on a two-dimensional array ==



<source lang="java">
public class MainClass {
public static void main(String args[]) {
int sum = 0;
int nums[][] = new int[3][5];
// give nums some values
for (int i = 0; i < 3; i++)
for (int j = 0; j < 5; j++)
nums[i][j] = (i + 1) * (j + 1);
// use for-each for to display and sum the values
for (int x[] : nums) {
for (int y : x) {
System.out.println("Value is: " + y);
sum += y;
}
}
System.out.println("Summation: " + sum);
}
}</source>



<pre class=codeResult>Value is: 1
Value is: 2
Value is: 3
Value is: 4
Value is: 5
Value is: 2
Value is: 4
Value is: 6
Value is: 8
Value is: 10
Value is: 3
Value is: 6
Value is: 9
Value is: 12
Value is: 15
Summation: 90</pre>

== The for each loop for an enum data type ==



<source lang="java">
for (type identifier : iterable_expression) {
// statements
}</source>



<pre class=codeResult>The season is now spring
The season is now summer
The season is now fall
The season is now winter</pre>

== The for-each loop is essentially read-only ==



<source lang="java">
public class MainClass {
public static void main(String args[]) {
int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

for(int x : nums) {
System.out.print(x + " ");
x = x * 10; // no effect on nums
}

System.out.println();
for(int x : nums)
System.out.print(x + " ");
System.out.println();
}
}</source>



<pre class=codeResult>1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10</pre>

== The For-Each Version of the for Loop ==

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



<source lang="java">
for(type itr-var : iterableObj) statement-block</source>



The object referred to by iterableObj must be an array or
an object that implements the new Iterable interface.

== Use a for-each style for loop ==



<source lang="java">
public class MainClass {
public static void main(String args[]) {
int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int sum = 0;
// use for-each style for to display and sum the values
for(int x : nums) {
System.out.println("Value is: " + x);
sum += x;
}
System.out.println("Summation: " + sum);
}
}</source>



<pre class=codeResult>Value is: 1
Value is: 2
Value is: 3
Value is: 4
Value is: 5
Value is: 6
Value is: 7
Value is: 8
Value is: 9
Value is: 10
Summation: 55</pre>

== Using break with a for-each-style for ==



<source lang="java">
public class MainClass {
public static void main(String args[]) {
int sum = 0;
int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
// Use for to display and sum the values.
for (int x : nums) {
System.out.println("Value is: " + x);
sum += x;
if (x == 5){
break; // stop the loop when 5 is obtained
}
}
System.out.println("Summation of first 5 elements: " + sum);
}
}</source>



<pre class=codeResult>Value is: 1
Value is: 2
Value is: 3
Value is: 4
Value is: 5
Summation of first 5 elements: 15</pre>

== Using "for each" to loop through array ==



<source lang="java">
public class MainClass {
public static void main(String[] arg) {
char[] vowels = { "a", "e", "i", "o", "u"};

for(char ch: vowels){
System.out.println(ch);
}
}
}</source>



<pre class=codeResult>a
e
i
o
u</pre>

== Using the For-Each Loop with Collections: ArrayList ==

For-Each Loop can be used to any object that implements the Iterable interface.
This includes all collections defined by the Collections Framework,



<source lang="java">
import java.util.ArrayList;

public class MainClass {

public static void main(String args[]) {
ArrayList<Double> list = new ArrayList<Double>();
list.add(10.14);
list.add(20.22);
list.add(30.78);
list.add(40.46);
double sum = 0.0;
for(double itr : list)
sum = sum + itr;
System.out.println(sum);

}
}</source>



<pre class=codeResult>101.6</pre>

← Предыдущая	Версия 05:19, 1 июня 2010
(нет различий)

Java Tutorial/Statement Control/For Each Loop - История изменений

Admin: 1 версия

в 17:44, 31 мая 2010