Java Tutorial/Development/Random
Содержание
- 1 Create two random number generators with the same seed
- 2 Generate a random array of numbers
- 3 Generating Random integer Numbers
- 4 Operations for random Strings
- 5 Random boolean
- 6 Random bytes
- 7 Random double type number
- 8 Random float type number
- 9 Random Gaussian values.
- 10 Random integers that range from from 0 to n
- 11 Random long type number
- 12 Random.nextInt(n) returns a distributed int value between 0 (inclusive) and n (exclusive).
- 13 Random number between 0 AND 10
- 14 Random numbers between 0.0 and 1.0
- 15 Roll a six-sided die imes
Create two random number generators with the same seed
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); long seed = rand.nextLong(); rand = new Random(seed); Random rand2 = new Random(seed); }
}</source>
Generate a random array of numbers
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] args) { Random r = new Random(); // generate some random boolean values boolean[] booleans = new boolean[10]; for (int i = 0; i < booleans.length; i++) { booleans[i] = r.nextBoolean(); } for (boolean b : booleans) { System.out.print(b + ", "); } // generate a uniformly distributed int random numbers int[] integers = new int[10]; for (int i = 0; i < integers.length; i++) { integers[i] = r.nextInt(); } for (int i : integers) { System.out.print(i + ", "); } // generate a uniformly distributed float random numbers float[] floats = new float[10]; for (int i = 0; i < floats.length; i++) { floats[i] = r.nextFloat(); } for (float f : floats) { System.out.print(f + ", "); } // generate a Gaussian normally distributed random numbers double[] gaussians = new double[10]; for (int i = 0; i < gaussians.length; i++) { gaussians[i] = r.nextGaussian(); } for (double d : gaussians) { System.out.print(d + ", "); } }
}</source>
Generating Random integer Numbers
<source lang="java">
import java.util.Random; public class MainClass {
public static void main(String[] args) { Random diceValues = new Random(); System.out.println(diceValues.nextInt(6)); System.out.println(diceValues.nextInt(6)); }
}</source>
5 3
Operations for random Strings
<source lang="java">
/*
* Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */
import java.util.Random; /**
* Operations for random String
s.
* Currently private high surrogate characters are ignored.
* These are unicode characters that fall between the values 56192 (db80)
* and 56319 (dbff) as we don"t know how to handle them.
* High and low surrogates are correctly dealt with - that is if a
* high surrogate is randomly chosen, 55296 (d800) to 56191 (db7f)
* then it is followed by a low surrogate. If a low surrogate is chosen,
* 56320 (dc00) to 57343 (dfff) then it is placed after a randomly
* chosen high surrogate.
*
* @author
* @author Stephen Colebourne
* @author Gary Gregory
* @author Phil Steitz
* @since 1.0
* @version $Id: RandomStringUtils.java 471626 2006-11-06 04:02:09Z bayard $
*/
public class RandomStringUtils {
/** * Random object used by random method. This has to be not local * to the random method so as to not return the same value in the * same millisecond. */ private static final Random RANDOM = new Random(); /** *RandomStringUtils
instances should NOT be constructed in * standard programming. Instead, the class should be used as *RandomStringUtils.random(5);
. * * This constructor is public to permit tools that require a JavaBean instance * to operate. */ public RandomStringUtils() { super(); } // Random //----------------------------------------------------------------------- /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of all characters. * * @param count the length of random string to create * @return the random string */ public static String random(int count) { return random(count, false, false); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of characters whose * ASCII value is between32
and126
(inclusive). * * @param count the length of random string to create * @return the random string */ public static String randomAscii(int count) { return random(count, 32, 127, false, false); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of alphabetic * characters. * * @param count the length of random string to create * @return the random string */ public static String randomAlphabetic(int count) { return random(count, true, false); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of alpha-numeric * characters. * * @param count the length of random string to create * @return the random string */ public static String randomAlphanumeric(int count) { return random(count, true, true); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of numeric * characters. * * @param count the length of random string to create * @return the random string */ public static String randomNumeric(int count) { return random(count, false, true); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of alpha-numeric * characters as indicated by the arguments. * * @param count the length of random string to create * @param letters iftrue
, generated string will include * alphabetic characters * @param numbers iftrue
, generated string will include * numeric characters * @return the random string */ public static String random(int count, boolean letters, boolean numbers) { return random(count, 0, 0, letters, numbers); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of alpha-numeric * characters as indicated by the arguments. * * @param count the length of random string to create * @param start the position in set of chars to start at * @param end the position in set of chars to end before * @param letters iftrue
, generated string will include * alphabetic characters * @param numbers iftrue
, generated string will include * numeric characters * @return the random string */ public static String random(int count, int start, int end, boolean letters, boolean numbers) { return random(count, start, end, letters, numbers, null, RANDOM); } /** * Creates a random string based on a variety of options, using * default source of randomness. * * This method has exactly the same semantics as * {@link #random(int,int,int,boolean,boolean,char[],Random)}, but * instead of using an externally supplied source of randomness, it uses * the internal static {@link Random} instance. * * @param count the length of random string to create * @param start the position in set of chars to start at * @param end the position in set of chars to end before * @param letters only allow letters? * @param numbers only allow numbers? * @param chars the set of chars to choose randoms from. * Ifnull
, then it will use the set of all chars. * @return the random string * @throws ArrayIndexOutOfBoundsException if there are not *(end - start) + 1
characters in the set array. */ public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars) { return random(count, start, end, letters, numbers, chars, RANDOM); } /** * Creates a random string based on a variety of options, using * supplied source of randomness. * * If start and end are both0
, start and end are set * to" "
and"z"
, the ASCII printable * characters, will be used, unless letters and numbers are both *false
, in which case, start and end are set to *0
andInteger.MAX_VALUE
. * * If set is notnull
, characters between start and * end are chosen. * * This method accepts a user-supplied {@link Random} * instance to use as a source of randomness. By seeding a single * {@link Random} instance with a fixed seed and using it for each call, * the same random sequence of strings can be generated repeatedly * and predictably. * * @param count the length of random string to create * @param start the position in set of chars to start at * @param end the position in set of chars to end before * @param letters only allow letters? * @param numbers only allow numbers? * @param chars the set of chars to choose randoms from. * Ifnull
, then it will use the set of all chars. * @param random a source of randomness. * @return the random string * @throws ArrayIndexOutOfBoundsException if there are not *(end - start) + 1
characters in the set array. * @throws IllegalArgumentException ifcount
< 0. * @since 2.0 */ public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars, Random random) { if (count == 0) { return ""; } else if (count < 0) { throw new IllegalArgumentException("Requested random string length " + count + " is less than 0."); } if ((start == 0) && (end == 0)) { end = "z" + 1; start = " "; if (!letters && !numbers) { start = 0; end = Integer.MAX_VALUE; } } char[] buffer = new char[count]; int gap = end - start; while (count-- != 0) { char ch; if (chars == null) { ch = (char) (random.nextInt(gap) + start); } else { ch = chars[random.nextInt(gap) + start]; } if ((letters && Character.isLetter(ch)) || (numbers && Character.isDigit(ch)) || (!letters && !numbers)) { if(ch >= 56320 && ch <= 57343) { if(count == 0) { count++; } else { // low surrogate, insert high surrogate after putting it in buffer[count] = ch; count--; buffer[count] = (char) (55296 + random.nextInt(128)); } } else if(ch >= 55296 && ch <= 56191) { if(count == 0) { count++; } else { // high surrogate, insert low surrogate before putting it in buffer[count] = (char) (56320 + random.nextInt(128)); count--; buffer[count] = ch; } } else if(ch >= 56192 && ch <= 56319) { // private high surrogate, no effing clue, so skip it count++; } else { buffer[count] = ch; } } else { count++; } } return new String(buffer); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of characters * specified. * * @param count the length of random string to create * @param chars the String containing the set of characters to use, * may be null * @return the random string * @throws IllegalArgumentException ifcount
< 0. */ public static String random(int count, String chars) { if (chars == null) { return random(count, 0, 0, false, false, null, RANDOM); } return random(count, chars.toCharArray()); } /** * Creates a random string whose length is the number of characters * specified. * * Characters will be chosen from the set of characters specified. * * @param count the length of random string to create * @param chars the character array containing the set of characters to use, * may be null * @return the random string * @throws IllegalArgumentException ifcount
< 0. */ public static String random(int count, char[] chars) { if (chars == null) { return random(count, 0, 0, false, false, null, RANDOM); } return random(count, 0, chars.length, false, false, chars, RANDOM); }
}</source>
Random boolean
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); boolean b = rand.nextBoolean(); long l = rand.nextLong(); float f = rand.nextFloat(); // 0.0 <= f < 1.0 double d = rand.nextDouble(); // 0.0 <= d < 1.0 }
}</source>
Random bytes
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); byte[] bytes = new byte[5]; rand.nextBytes(bytes); }
}</source>
Random double type number
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); boolean b = rand.nextBoolean(); long l = rand.nextLong(); float f = rand.nextFloat(); // 0.0 <= f < 1.0 double d = rand.nextDouble(); // 0.0 <= d < 1.0 }
}</source>
Random float type number
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); boolean b = rand.nextBoolean(); long l = rand.nextLong(); float f = rand.nextFloat(); // 0.0 <= f < 1.0 double d = rand.nextDouble(); // 0.0 <= d < 1.0 }
}</source>
Random Gaussian values.
<source lang="java">
import java.util.Random; class RandDemo {
public static void main(String args[]) { Random r = new Random(); double val; double sum = 0; int bell[] = new int[10]; for (int i = 0; i < 100; i++) { val = r.nextGaussian(); sum += val; double t = -2; for (int x = 0; x < 10; x++, t += 0.5) if (val < t) { bell[x]++; break; } } System.out.println("Average of values: " + (sum / 100)); for (int i = 0; i < 10; i++) { for (int x = bell[i]; x > 0; x--) System.out.print("*"); System.out.println(); } }
}</source>
Random integers that range from from 0 to n
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); int n = 10; int i = rand.nextInt(n + 1); System.out.println(i); }
}</source>
Random long type number
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) throws Exception { Random rand = new Random(); boolean b = rand.nextBoolean(); long l = rand.nextLong(); float f = rand.nextFloat(); // 0.0 <= f < 1.0 double d = rand.nextDouble(); // 0.0 <= d < 1.0 }
}</source>
Random.nextInt(n) returns a distributed int value between 0 (inclusive) and n (exclusive).
<source lang="java">
// random number between 0 AND 10 import java.util.Random; public class Main {
public static void main(String[] argv) { Random r = new Random(); int randint = r.nextInt(10); System.out.println(randint); }
}</source>
Random number between 0 AND 10
<source lang="java">
import java.util.Random; public class Main {
public static void main(String[] argv) { Random r = new Random(); int randint = Math.abs(r.nextInt()) % 11; System.out.println(randint); }
}</source>
Random numbers between 0.0 and 1.0
<source lang="java">
public class Main {
public static void main(String[] args) { for (int i = 0; i < 5; i++){ System.out.println("Random Number [" + (i + 1) + "] : " + Math.random()); } }
}</source>
Roll a six-sided die imes
<source lang="java">
import java.util.Random; public class MainClass {
public static void main( String args[] ) { Random randomNumbers = new Random(); // random number generator int frequency1 = 0; // count of 1s rolled int frequency2 = 0; // count of 2s rolled int frequency3 = 0; // count of 3s rolled int frequency4 = 0; // count of 4s rolled int frequency5 = 0; // count of 5s rolled int frequency6 = 0; // count of 6s rolled int face; // stores most recently rolled value // summarize results of 6000 rolls of a die for ( int roll = 1; roll <= 6000; roll++ ) { face = 1 + randomNumbers.nextInt( 6 ); // number from 1 to 6 // determine roll value 1-6 and increment appropriate counter switch ( face ) { case 1: ++frequency1; // increment the 1s counter break; case 2: ++frequency2; // increment the 2s counter break; case 3: ++frequency3; // increment the 3s counter break; case 4: ++frequency4; // increment the 4s counter break; case 5: ++frequency5; // increment the 5s counter break; case 6: ++frequency6; // increment the 6s counter break; // optional at end of switch } } System.out.println( "Face\tFrequency" ); // output headers System.out.printf( "1\t%d\n2\t%d\n3\t%d\n4\t%d\n5\t%d\n6\t%d\n", frequency1, frequency2, frequency3, frequency4, frequency5, frequency6 ); }
}</source>
Face Frequency 1 1005 2 1028 3 1027 4 989 5 994 6 957