Java example source code file (RandomStringUtilsTest.java)

This example Java source code file (RandomStringUtilsTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

charset, constructor, dummy, expected, iae, illegalargumentexception, message, random, randomstringutilstest, reflection, string, test, utf-8, util

The RandomStringUtilsTest.java Java example source code

/*
 * 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.
 */
package org.apache.commons.lang3;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;
import java.nio.charset.Charset;
import java.util.Random;

import org.junit.Test;

/**
 * Unit tests {@link org.apache.commons.lang3.RandomStringUtils}.
 */
public class RandomStringUtilsTest {

    //-----------------------------------------------------------------------
    @Test
    public void testConstructor() {
        assertNotNull(new RandomStringUtils());
        final Constructor<?>[] cons = RandomStringUtils.class.getDeclaredConstructors();
        assertEquals(1, cons.length);
        assertTrue(Modifier.isPublic(cons[0].getModifiers()));
        assertTrue(Modifier.isPublic(RandomStringUtils.class.getModifiers()));
        assertFalse(Modifier.isFinal(RandomStringUtils.class.getModifiers()));
    }
    
    //-----------------------------------------------------------------------
    /**
     * Test the implementation
     */
    @Test
    public void testRandomStringUtils() {
        String r1 = RandomStringUtils.random(50);
        assertEquals("random(50) length", 50, r1.length());
        String r2 = RandomStringUtils.random(50);
        assertEquals("random(50) length", 50, r2.length());
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.randomAscii(50);
        assertEquals("randomAscii(50) length", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("char between 32 and 127", r1.charAt(i) >= 32 && r1.charAt(i) <= 127);
        }        
        r2 = RandomStringUtils.randomAscii(50);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));

        r1 = RandomStringUtils.randomAlphabetic(50);
        assertEquals("randomAlphabetic(50)", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("r1 contains alphabetic", Character.isLetter(r1.charAt(i)) && !Character.isDigit(r1.charAt(i)));
        }
        r2 = RandomStringUtils.randomAlphabetic(50);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.randomAlphanumeric(50);
        assertEquals("randomAlphanumeric(50)", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("r1 contains alphanumeric", Character.isLetterOrDigit(r1.charAt(i)));
        }
        r2 = RandomStringUtils.randomAlphabetic(50);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.randomGraph(50);
        assertEquals("randomGraph(50) length", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("char between 33 and 126", r1.charAt(i) >= 33 && r1.charAt(i) <= 126);
        }
        r2 = RandomStringUtils.randomGraph(50);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.randomNumeric(50);
        assertEquals("randomNumeric(50)", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("r1 contains numeric", Character.isDigit(r1.charAt(i)) && !Character.isLetter(r1.charAt(i)));
        }
        r2 = RandomStringUtils.randomNumeric(50);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.randomPrint(50);
        assertEquals("randomPrint(50) length", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("char between 32 and 126", r1.charAt(i) >= 32 && r1.charAt(i) <= 126);
        }
        r2 = RandomStringUtils.randomPrint(50);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        String set = "abcdefg";
        r1 = RandomStringUtils.random(50, set);
        assertEquals("random(50, \"abcdefg\")", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("random char in set", set.indexOf(r1.charAt(i)) > -1);
        }
        r2 = RandomStringUtils.random(50, set);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.random(50, (String) null);
        assertEquals("random(50) length", 50, r1.length());
        r2 = RandomStringUtils.random(50, (String) null);
        assertEquals("random(50) length", 50, r2.length());
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        set = "stuvwxyz";
        r1 = RandomStringUtils.random(50, set.toCharArray());
        assertEquals("random(50, \"stuvwxyz\")", 50, r1.length());
        for(int i = 0; i < r1.length(); i++) {
            assertTrue("random char in set", set.indexOf(r1.charAt(i)) > -1);
        }
        r2 = RandomStringUtils.random(50, set);
        assertTrue("!r1.equals(r2)", !r1.equals(r2));
        
        r1 = RandomStringUtils.random(50, (char[]) null);
        assertEquals("random(50) length", 50, r1.length());
        r2 = RandomStringUtils.random(50, (char[]) null);
        assertEquals("random(50) length", 50, r2.length());
        assertTrue("!r1.equals(r2)", !r1.equals(r2));

        final long seed = System.currentTimeMillis();
        r1 = RandomStringUtils.random(50,0,0,true,true,null,new Random(seed));
        r2 = RandomStringUtils.random(50,0,0,true,true,null,new Random(seed));
        assertEquals("r1.equals(r2)", r1, r2);

        r1 = RandomStringUtils.random(0);
        assertEquals("random(0).equals(\"\")", "", r1);
    }

    @Test
    public void testLANG805() {
        final long seed = System.currentTimeMillis();
        assertEquals("aaa", RandomStringUtils.random(3,0,0,false,false,new char[]{'a'},new Random(seed)));
    }

    @Test
    public void testLANG807() {
        try {
            RandomStringUtils.random(3,5,5,false,false);
            fail("Expected IllegalArgumentException");
        } catch (final IllegalArgumentException ex) { // distinguish from Random#nextInt message
            final String msg = ex.getMessage();
            assertTrue("Message (" + msg + ") must contain 'start'", msg.contains("start"));
            assertTrue("Message (" + msg + ") must contain 'end'", msg.contains("end"));
        }
    }

    @Test
    public void testExceptions() {
        final char[] DUMMY = new char[]{'a'}; // valid char array
        try {
            RandomStringUtils.random(-1);
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, true, true);
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, DUMMY);
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(1, new char[0]); // must not provide empty array => IAE
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, "");
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, (String)null);
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, 'a', 'z', false, false);
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, 'a', 'z', false, false, DUMMY);
            fail();
        } catch (final IllegalArgumentException ex) {}
        try {
            RandomStringUtils.random(-1, 'a', 'z', false, false, DUMMY, new Random());
            fail();
        } catch (final IllegalArgumentException ex) {}
    }
    
    /**
     * Make sure boundary alphanumeric characters are generated by randomAlphaNumeric
     * This test will fail randomly with probability = 6 * (61/62)**1000 ~ 5.2E-7
     */  
    @Test
    public void testRandomAlphaNumeric() {
        final char[] testChars = {'a', 'z', 'A', 'Z', '0', '9'};
        final boolean[] found = {false, false, false, false, false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomAlphanumeric(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            if (!found[i]) {
                fail("alphanumeric character not generated in 1000 attempts: " 
                   + testChars[i] +" -- repeated failures indicate a problem ");
            }
        }
    }
    
    /**
     * Make sure '0' and '9' are generated by randomNumeric
     * This test will fail randomly with probability = 2 * (9/10)**1000 ~ 3.5E-46
     */  
    @Test
    public void testRandomNumeric() {
        final char[] testChars = {'0','9'};
        final boolean[] found = {false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomNumeric(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            if (!found[i]) {
                fail("digit not generated in 1000 attempts: " 
                   + testChars[i] +" -- repeated failures indicate a problem ");
            }
        }  
    }
    
    /**
     * Make sure boundary alpha characters are generated by randomAlphabetic
     * This test will fail randomly with probability = 4 * (51/52)**1000 ~ 1.58E-8
     */  
    @Test
    public void testRandomAlphabetic() {
        final char[] testChars = {'a', 'z', 'A', 'Z'};
        final boolean[] found = {false, false, false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomAlphabetic(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            if (!found[i]) {
                fail("alphanumeric character not generated in 1000 attempts: " 
                   + testChars[i] +" -- repeated failures indicate a problem ");
            }
        }
    }
    
    /**
     * Make sure 32 and 127 are generated by randomNumeric
     * This test will fail randomly with probability = 2*(95/96)**1000 ~ 5.7E-5
     */  
    @Test
    public void testRandomAscii() {
        final char[] testChars = {(char) 32, (char) 126};
        final boolean[] found = {false, false};
        for (int i = 0; i < 100; i++) {
            final String randString = RandomStringUtils.randomAscii(10);
            for (int j = 0; j < testChars.length; j++) {
                if (randString.indexOf(testChars[j]) > 0) {
                    found[j] = true;
                }
            }
        }
        for (int i = 0; i < testChars.length; i++) {
            if (!found[i]) {
                fail("ascii character not generated in 1000 attempts: " 
                + (int) testChars[i] + 
                 " -- repeated failures indicate a problem");
            }
        }  
    }
    
    /** 
     * Test homogeneity of random strings generated --
     * i.e., test that characters show up with expected frequencies
     * in generated strings.  Will fail randomly about 1 in 1000 times.
     * Repeated failures indicate a problem.
     */
    @Test
    public void testRandomStringUtilsHomog() {
        final String set = "abc";
        final char[] chars = set.toCharArray();
        String gen = "";
        final int[] counts = {0,0,0};
        final int[] expected = {200,200,200};
        for (int i = 0; i< 100; i++) {
           gen = RandomStringUtils.random(6,chars);
           for (int j = 0; j < 6; j++) {
               switch (gen.charAt(j)) {
                   case 'a': {counts[0]++; break;}
                   case 'b': {counts[1]++; break;}
                   case 'c': {counts[2]++; break;}
                   default: {fail("generated character not in set");}
               }
           }
        } 
        // Perform chi-square test with df = 3-1 = 2, testing at .001 level
        assertTrue("test homogeneity -- will fail about 1 in 1000 times",
            chiSquare(expected,counts) < 13.82);  
    }
    
    /**
     * Computes Chi-Square statistic given observed and expected counts
     * @param observed array of observed frequency counts
     * @param expected array of expected frequency counts
     */
    private double chiSquare(final int[] expected, final int[] observed) {
        double sumSq = 0.0d;
        double dev = 0.0d;
        for (int i = 0; i < observed.length; i++) {
            dev = observed[i] - expected[i];
            sumSq += dev * dev / expected[i];
        }
        return sumSq;
    }           

    /**
     * Checks if the string got by {@link RandomStringUtils#random(int)}
     * can be converted to UTF-8 and back without loss.
     *
     * @see <a href="http://issues.apache.org/jira/browse/LANG-100">LANG-100
     */
    @Test
    public void testLang100() {
        final int size = 5000;
        final Charset charset = Charset.forName("UTF-8");
        final String orig = RandomStringUtils.random(size);
        final byte[] bytes = orig.getBytes(charset);
        final String copy = new String(bytes, charset);

        // for a verbose compare:
        for (int i=0; i < orig.length() && i < copy.length(); i++) {
            final char o = orig.charAt(i);
            final char c = copy.charAt(i);
            assertEquals("differs at " + i + "(" + Integer.toHexString(new Character(o).hashCode()) + "," +
            Integer.toHexString(new Character(c).hashCode()) + ")", o, c);
        }
        // compare length also
        assertEquals(orig.length(), copy.length());
        // just to be complete
        assertEquals(orig, copy);
    }
}