Guava - Longs Class

Longs is a utility class for primitive type long.

Class Declaration

Following is the declaration for com.google.common.primitives.Longs class −

@GwtCompatible
public final class Longs
   extends Object

Class Fields

Sr.No	Field & Description
1	static int BYTES The number of bytes required to represent a primitive long value.
2	static long MAX_POWER_OF_TWO The largest power of two that can be represented as a long.

Class Methods

Sr.No	Method & Description
1	static List<Long> asList(long... backingArray) Returns a fixed-size list backed by the specified array, similar to Arrays.asList(Object[]).
2	static int compare(long a, long b) Compares the two specified long values.
3	static long[] concat(long[]... arrays) Returns the values from each provided array combined into a single array.
4	static boolean contains(long[] array, long target) Returns true if target is present as an element anywhere in array.
5	static long[] ensureCapacity(long[] array, int minLength, int padding) Returns an array containing the same values as array, but guaranteed to be of a specified minimum length.
6	static long fromByteArray(byte[] bytes) Returns the long value whose big-endian representation is stored in the first 8 bytes of bytes; equivalent to ByteBuffer.wrap(bytes).getLong().
7	static long fromBytes(byte b1, byte b2, byte b3, byte b4, byte b5, byte b6, byte b7, byte b8) Returns the long value whose byte representation is the given 8 bytes, in big-endian order; equivalent to Longs.fromByteArray(new byte[] {b1, b2, b3, b4, b5, b6, b7, b8}).
8	static int hashCode(long value) Returns a hash code for value; equal to the result of invoking ((Long) value).hashCode().
9	static int indexOf(long[] array, long target) Returns the index of the first appearance of the value target in array.
10	static int indexOf(long[] array, long[] target) Returns the start position of the first occurrence of the specified target within array, or -1 if there is no such occurrence.
11	static String join(String separator, long... array) Returns a string containing the supplied long values separated by separator.
12	static int lastIndexOf(long[] array, long target) Returns the index of the last appearance of the value target in array.
13	static Comparator<long[]> lexicographicalComparator() Returns a comparator that compares two long arrays lexicographically.
14	static long max(long... array) Returns the greatest value present in array.
15	static long min(long... array) Returns the least value present in array.
16	static Converter<String,Long> stringConverter() Returns a serializable converter object that converts between strings and longs using Long.decode(java.lang.String) and Long.toString().
17	static long[] toArray(Collection<? extends Number> collection) Returns an array containing each value of collection, converted to a long value in the manner of Number.longValue().
18	static byte[] toByteArray(long value) Returns a big-endian representation of value in an 8-element byte array; equivalent to ByteBuffer.allocate(8).putLong(value).array().
19	static Long tryParse(String string) Parses the specified string as a signed decimal long value.

Methods Inherited

This class inherits methods from the following class −

• java.lang.Object

Example - Converting Array of Long to List and vice versa

GuavaTester.java

package com.tutorialspoint;

import java.util.List;

import com.google.common.primitives.Longs;

public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testLongs();
   }

   private void testLongs() {
      long[] longArray = {1,2,3,4,5,6,7,8,9};

      //convert array of primitives to array of objects
      List<Long> objectArray = Longs.asList(longArray);
      System.out.println(objectArray.toString());

      //convert array of objects to array of primitives
      longArray = Longs.toArray(objectArray);
      System.out.print("[ ");
      
      for(int i = 0; i< longArray.length ; i++) {
         System.out.print(longArray[i] + " ");
      }
      
      System.out.println("]");
   }
}

Output

Run the GuavaTester and verify the output.

[1, 2, 3, 4, 5, 6, 7, 8, 9]
[ 1 2 3 4 5 6 7 8 9 ]

Example - Checking Presence of Element in Array of Longs

GuavaTester.java

package com.tutorialspoint;

import com.google.common.primitives.Longs;

public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testLongs();
   }

   private void testLongs() {
      long[] longArray = {1,2,3,4,5,6,7,8,9};
      
      //check if element is present in the list of primitives or not
      System.out.println("5 is in list? "+ Longs.contains(longArray, 5L));
	  System.out.println("10 is in list? "+ Longs.contains(longArray, 10L));
   }
}

Output

Run the GuavaTester and verify the output.

5 is in list? true
10 is in list? false

Example - Getting Minimum/Maximum from an Array of Longs

GuavaTester.java

package com.tutorialspoint;

import com.google.common.primitives.Longs;

public class GuavaTester {
   public static void main(String args[]) {
      GuavaTester tester = new GuavaTester();
      tester.testLongs();
   }

   private void testLongs() {
      long[] longArray = {1,2,3,4,5,6,7,8,9};

      //Returns the minimum		
      System.out.println("Min: " + Longs.min(longArray));

      //Returns the maximum		
      System.out.println("Max: " + Longs.max(longArray));

      //get the byte array from an integer
      byte[] byteArray = Longs.toByteArray(20000);
      
      for(int i = 0; i< byteArray.length ; i++) {
         System.out.print(byteArray[i] + " ");
      }
   }
}

Output

Run the GuavaTester and verify the output.

Min: 1
Max: 9
0 0 0 0 0 0 78 32