Java masīvs ir datu struktūra, kurā varam uzglabāt viena un tā paša datu tipa elementus. Masīva elementi tiek glabāti blakus esošā atmiņas vietā. Tātad, mēs varam saglabāt fiksētu elementu kopu masīvā.
Ir šādi veidi, kā drukāt masīvu Java:
- Java priekš cilpa
- Java katram cilpa
- Java Arrays.toString() metodi
- Java Arrays.deepToString() metodi
- Java Arrays.asList() metodi
- Java Iterators Interfeiss
- Java Straume API
Java cilpai
Java priekš cilpa tiek izmantota, lai atkārtoti izpildītu paziņojumu kopu, līdz tiek izpildīts konkrēts nosacījums.
kā atgriezt masīvu java
Sintakse:
for(initialization; condition; increment/ decrement) { //statements } For cilpas piemērs
Nākamajā piemērā esam izveidojuši četru garumu masīvu un inicializējām tajā elementus. Mēs esam izmantojuši cilpu, lai iegūtu vērtības no masīva. Tas ir vispopulārākais veids, kā drukāt masīvu Java.
public class PrintArrayExample1 { public static void main(String args[]) { //declaration and instantiation of an array int arr[]=new int[4]; //initializing elements arr[0]=10; arr[1]=20; arr[2]=70; arr[3]=40; //traversing over array using for loop for(int i=0;i <arr.length;i++) length is the property of array system.out.println(arr[i]); } < pre> <p> <strong>Output:</strong> </p> <pre> 10 20 70 40 </pre> <h2>Java for-each loop</h2> <p>Java <strong>for-each</strong> loop is also used to traverse over an array or collection. It works on the basis of elements. It returns elements one by one in the defined variable. </p> <p> <strong>Syntax:</strong> </p> <pre> for(Type var:array) </pre> <p> <strong>Example of for-each loop</strong> </p> <p>In the following example, we have created an array of String type of length four and initialized elements into it. We have used for-each loop to traverse over the array.</p> <pre> public class PrintArrayExample2 { public static void main(String args[]) { // declaration and instantiation of an array String[] city = new String[4]; //initializing elements city[0] = 'Delhi'; city[1] = 'Jaipur'; city[2] = 'Gujarat'; city[3] = 'Mumbai'; //traversing over array using for-each loop for (String str : city) { System.out.println(str); } } } </pre> <p> <strong>Output:</strong> </p> <pre> Delhi Jaipur Gujarat Mumbai </pre> <h2>Java Arrays.toString() method</h2> <p>Java <strong>Arrays.toString()</strong> is a static method of <strong>Arrays </strong> class which belongs to <strong>java.util </strong> package It contains various methods for manipulating array. </p> <p> <strong>Syntax:</strong> </p> <pre> public static String toString(int[] a) </pre> <p>It accepts an array of any primitive type as an argument. It returns a <strong>string</strong> representation of an array that contains a list of array's elements. The elements of an array are converted to String by <strong>String.valueOf(int) </strong> .</p> <p> <strong>Example of toString() method</strong> </p> <pre> import java.util.Arrays; public class PrintArrayExample3 { public static void main(String[] args) { //declaring and initializing array int array[] = {34,-10, 56, -9, -33}; //returns string representation of the specified array System.out.println(Arrays.toString(array)); } } </pre> <p> <strong>Output:</strong> </p> <pre> [34, -10, 56, -9, -33] </pre> <h2>Java Arrays.deepToString() method</h2> <p>The <strong>deepToString()</strong> method of Java Arrays class is designed for converting multidimensional arrays to strings.</p> <p> <strong>Syntax:</strong> </p> <pre> public static String deepToString(Object[] a) </pre> <p>It accepts an array as a parameter. It returns the String representation of an array.</p> <p> <strong>Example of deepToString() method</strong> </p> <p>In the following example, we have created a two dimensional array of float type. </p> <pre> import java.util.Arrays; public class PrintArrayExample4 { public static void main(String[] args) { //declaration and initialization of two dimensional array of float type float[][] array = {{1.2f, 2.5f}, {3.9f, 4.0f}, {5.3f, 6.2f}}; System.out.println(Arrays.deepToString(array)); } } </pre> <p> <strong>Output:</strong> </p> <pre> [[1.2, 2.5], [3.9, 4.0], [5.3, 6.2]] </pre> <h2>Java Arrays.asList() method</h2> <p>Java <strong>Arrays.asList()</strong> is a static method of Java <strong>Arrays</strong> class which belongs to <strong>java.util</strong> package. It act as a bridge between array based and collection based API. </p> <p> <strong>Syntax:</strong> </p> <pre> public static ListasList(T...a) </pre> <p>The method also provides an easy way to create a fixed-size list initialize to contain many elements.</p> <pre> List obj=Arrays.toString(array[] a </pre> <p>It accepts an array as an argument. It returns the list view of an array.</p> <p> <strong>Example of asList() method</strong> </p> <pre> import java.util.Arrays; public class PrintArrayExample5 { public static void main(String [] args) { //declaration and initialization of two dimensional array String[] stringArray={'Hello','Java','Programmers'}; System.out.println(Arrays.asList(stringArray)); } </pre> <p> <strong>Output:</strong> </p> <pre> [Hello, Java, Programmers] </pre> <h2>Java Iterator interface</h2> <p>Java <strong>Iterator</strong> is an interface which belongs to <strong>java.util</strong> package. The Iterator object can be created by calling iterator() method. It is present in Collection interface. It returns an iterator.</p> <p> <strong>Example of Iterator interface</strong> </p> <p>In the following, example, we have declare an array and initialize elements into it. We first convert the specified array into list by using Arrays.asList() method because iterator allows us to traverse over the collection and then invoke iterator() method of collection class.</p> <pre> import java.util.Arrays; import java.util.Iterator; public class PrintArrayExample6 { public static void main(String[] args) { //declaration and initialization of an array of Double type Double[] array = { 1.5, 2.6, 3.7, 4.8, 5.9}; //returns an iterator Iterator it = Arrays.asList(array).iterator(); while(itr.hasNext()) //returns a boolean value { System.out.println(itr.next()); } } } </pre> <p> <strong>Output:</strong> </p> <pre> 1.5 2.6 3.7 4.8 5.9 </pre> <h2>Java Stream API</h2> <p>A Java Stream is a data structure which is computed on-demand. It doesn't store data. It operates on the source data structure such as collection and array. Java stream API is used to implement internal iteration. It provides several features such as sequential and parallel execution. </p> <h3>Java stream() method</h3> <p>Java <strong>stream()</strong> is a static method of Java <strong>Arrays</strong> class which belongs to java.util package. It is used to get a sequential stream of an array.</p> <p> <strong>Syntax:</strong> </p> <pre> public static Stream stream(T[] array) </pre> <p>Where <strong>T</strong> is the type of array. The method accepts an <strong>array</strong> whose elements are to be converted into a sequential stream. It returns a sequential <strong>IntStream</strong> with the specified array as its source.</p> <h3>Java forEach() method</h3> <p>It is a terminal operation. It does not guarantee to respect the encounter order of the stream.</p> <p> <strong>Syntax:</strong> </p> <pre> void forEach(Consumer action) </pre> <p>The method accepts an <strong>action</strong> as a parameter. It is non-interfering action perform on each element. It does not return anything.</p> <p>There are two terminal operations which we can apply to a stream to print an array.</p> <p> <strong>Get an iterator to the stream</strong> </p> <pre> Iterator it=Arrays.stream(arr).iterator(); </pre> <p> <strong>Using stream().forEach()</strong> </p> <pre> Arrays.stream(arr).forEach(System.out::println); </pre> <p> <strong>Example of stream.forEach() method</strong> </p> <p>In the following example, we have used a different way to print an array. The forEach() method is used to iterate over every element of the stream. It is defined in the Iterable and Stream interface.</p> <p>Inside the forEach() method we have used System.out which is a reference to an object. It represent standard output stream. It has a method called println(). It is an overloaded method which can accept anything as an argument. When we put println() method after member access operator (::), it becomes an expression.</p> <pre> import java.util.Arrays; public class PrintArrayExample7 { public static void main(String[] args) { //declaration and initialization of an array of String type String[] arr = {'Java', 'C', 'C++', 'Python', 'Perl'}; //iterating by passing the method reference Arrays.stream(arr).forEach(System.out::println); } } </pre> <p> <strong>Output:</strong> </p> <pre> Java C C++ Python Perl </pre> <hr></arr.length;i++)> Java katrai cilpai
Java katram cilpa tiek izmantota arī, lai pārvietotos pa masīvu vai kolekciju. Tas darbojas, pamatojoties uz elementiem. Tas atgriež elementus pa vienam definētajā mainīgajā.
Sintakse:
for(Type var:array)
Katras cilpas piemērs
Nākamajā piemērā mēs esam izveidojuši virknes tipa masīvu ar četru garumu un inicializējām tajā elementus. Mēs esam izmantojuši katrai cilpai, lai pārvietotos pa masīvu.
public class PrintArrayExample2 { public static void main(String args[]) { // declaration and instantiation of an array String[] city = new String[4]; //initializing elements city[0] = 'Delhi'; city[1] = 'Jaipur'; city[2] = 'Gujarat'; city[3] = 'Mumbai'; //traversing over array using for-each loop for (String str : city) { System.out.println(str); } } } Izvade:
Delhi Jaipur Gujarat Mumbai
Java Arrays.toString() metode
Java Arrays.toString() ir statiska metode Masīvi klasei, kas pieder java.util pakete Tas satur dažādas metodes manipulēšanai ar masīvu.
Sintakse:
public static String toString(int[] a)
Tā pieņem jebkura primitīva veida masīvu kā argumentu. Tas atgriež a virkne masīva attēlojums, kas satur masīva elementu sarakstu. Masīva elementi tiek pārveidoti par String by String.valueOf(int) .
ToString() metodes piemērs
import java.util.Arrays; public class PrintArrayExample3 { public static void main(String[] args) { //declaring and initializing array int array[] = {34,-10, 56, -9, -33}; //returns string representation of the specified array System.out.println(Arrays.toString(array)); } } Izvade:
[34, -10, 56, -9, -33]
Java Arrays.deepToString() metode
The deepToString() Java Arrays klases metode ir paredzēta daudzdimensiju masīvu pārvēršanai virknēs.
Sintakse:
public static String deepToString(Object[] a)
Tas pieņem masīvu kā parametru. Tas atgriež masīva virknes attēlojumu.
DeepToString() metodes piemērs
Nākamajā piemērā mēs esam izveidojuši divdimensiju pludiņa tipa masīvu.
import java.util.Arrays; public class PrintArrayExample4 { public static void main(String[] args) { //declaration and initialization of two dimensional array of float type float[][] array = {{1.2f, 2.5f}, {3.9f, 4.0f}, {5.3f, 6.2f}}; System.out.println(Arrays.deepToString(array)); } } Izvade:
[[1.2, 2.5], [3.9, 4.0], [5.3, 6.2]]
Java Arrays.asList() metode
Java Arrays.asList() ir statiska Java metode Masīvi klasei, kas pieder java.util iepakojums. Tas darbojas kā tilts starp masīvu un kolekciju balstītu API.
Sintakse:
public static ListasList(T...a)
Šī metode nodrošina arī vienkāršu veidu, kā izveidot fiksēta izmēra saraksta inicializāciju, lai tajā būtu daudz elementu.
List obj=Arrays.toString(array[] a
Tas pieņem masīvu kā argumentu. Tas atgriež masīva saraksta skatu.
Metodes asList() piemērs
import java.util.Arrays; public class PrintArrayExample5 { public static void main(String [] args) { //declaration and initialization of two dimensional array String[] stringArray={'Hello','Java','Programmers'}; System.out.println(Arrays.asList(stringArray)); } Izvade:
[Hello, Java, Programmers]
Java Iterator interfeiss
Java Iterators ir saskarne, kas pieder java.util iepakojums. Iteratora objektu var izveidot, izsaucot iterator() metodi. Tas atrodas kolekcijas saskarnē. Tas atgriež iteratoru.
Iteratora saskarnes piemērs
Nākamajā piemērā mēs esam deklarējuši masīvu un inicializējuši tajā elementus. Vispirms mēs pārveidojam norādīto masīvu par sarakstu, izmantojot metodi Arrays.asList(), jo iterators ļauj mums šķērsot kolekciju un pēc tam izsaukt kolekcijas klases iterator() metodi.
import java.util.Arrays; import java.util.Iterator; public class PrintArrayExample6 { public static void main(String[] args) { //declaration and initialization of an array of Double type Double[] array = { 1.5, 2.6, 3.7, 4.8, 5.9}; //returns an iterator Iterator it = Arrays.asList(array).iterator(); while(itr.hasNext()) //returns a boolean value { System.out.println(itr.next()); } } } Izvade:
1.5 2.6 3.7 4.8 5.9
Java Stream API
Java straume ir datu struktūra, kas tiek aprēķināta pēc pieprasījuma. Tas neuzglabā datus. Tas darbojas ar avota datu struktūru, piemēram, kolekciju un masīvu. Java straumes API tiek izmantota iekšējās iterācijas ieviešanai. Tas nodrošina vairākas funkcijas, piemēram, secīgu un paralēlu izpildi.
Java straumes () metode
Java straume () ir statiska Java metode Masīvi klase, kas pieder java.util pakotnei. To izmanto, lai iegūtu secīgu masīva plūsmu.
Sintakse:
public static Stream stream(T[] array)
Kur T ir masīva veids. Metode pieņem an masīvs kuras elementi ir jāpārvērš secīgā plūsmā. Tas atgriež secīgu IntStream ar norādīto masīvu kā tā avotu.
Java forEach() metode
Tā ir termināļa darbība. Tas negarantē, ka tiks ievērota straumes tikšanās kārtība.
Sintakse:
void forEach(Consumer action)
Metode pieņem an darbība kā parametrs. Tā ir netraucējoša darbība, kas tiek veikta katram elementam. Tas neko neatdod.
Ir divas termināļa darbības, kuras mēs varam izmantot straumei, lai izdrukātu masīvu.
Iegūstiet straumes iteratoru
Iterator it=Arrays.stream(arr).iterator();
Izmantojot straumi().forEach()
Arrays.stream(arr).forEach(System.out::println);
Metodes stream.forEach() piemērs
Nākamajā piemērā mēs esam izmantojuši citu veidu, kā drukāt masīvu. Metode forEach() tiek izmantota, lai atkārtotu katru straumes elementu. Tas ir definēts interfeisā Iterable un Stream.
ForEach() metodē esam izmantojuši System.out, kas ir atsauce uz objektu. Tā ir standarta izvades plūsma. Tam ir metode, ko sauc par println(). Tā ir pārslogota metode, kas var pieņemt jebko kā argumentu. Ja aiz dalībnieka piekļuves operatora (::) ievietojam metodi println(), tā kļūst par izteiksmi.
import java.util.Arrays; public class PrintArrayExample7 { public static void main(String[] args) { //declaration and initialization of an array of String type String[] arr = {'Java', 'C', 'C++', 'Python', 'Perl'}; //iterating by passing the method reference Arrays.stream(arr).forEach(System.out::println); } } Izvade:
Java C C++ Python Perl