JAVA-22238 | moved articles into correct locations. (#14297)

core-java-modules/core-java-string-operations-6/README.md

@@ -3,3 +3,6 @@
 
 - [Find the Longest Word in a Given String in Java](https://www.baeldung.com/java-longest-word-string)
 - [Check if a String Is All Uppercase or Lowercase in Java](https://www.baeldung.com/java-check-string-uppercase-lowercase)
+- [Java – Generate Random String](https://www.baeldung.com/java-random-string)
+- [Fixing “constant string too long” Build Error](https://www.baeldung.com/java-constant-string-too-long-error)
+- [Compact Strings in Java 9](https://www.baeldung.com/java-9-compact-string)

core-java-modules/core-java-string-operations-6/src/main/java/com/baeldung/java9/compactstring/CompactStringDemo.java

@@ -0,0 +1,25 @@
+package com.baeldung.java9.compactstring;
+
+import java.util.List;
+import java.util.stream.IntStream;
+
+import static java.util.stream.Collectors.toList;
+
+public class CompactStringDemo {
+
+    public static void main(String[] args) {
+        long startTime = System.currentTimeMillis();
+        List strings = IntStream.rangeClosed(1, 10_000_000)
+          .mapToObj(Integer::toString).collect(toList());
+        long totalTime = System.currentTimeMillis() - startTime;
+        System.out.println("Generated " + strings.size() + " strings in "
+          + totalTime + " ms.");
+
+        startTime = System.currentTimeMillis();
+        String appended = (String) strings.stream().limit(100_000)
+          .reduce("", (left, right) -> left.toString() + right.toString());
+        totalTime = System.currentTimeMillis() - startTime;
+        System.out.println("Created string of length " + appended.length()
+          + " in " + totalTime + " ms.");
+    }
+}

core-java-modules/core-java-string-operations-6/src/test/java/com/baeldung/randomstrings/RandomStringsUnitTest.java

@@ -0,0 +1,103 @@
+package com.baeldung.randomstrings;
+
+import org.apache.commons.lang3.RandomStringUtils;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.nio.charset.Charset;
+import java.util.Random;
+
+public class RandomStringsUnitTest {
+
+    private static final Logger LOG = LoggerFactory.getLogger(RandomStringsUnitTest.class);
+
+    @Test
+    public void givenUsingPlainJava_whenGeneratingRandomStringUnbounded_thenCorrect() {
+        byte[] array = new byte[7]; // length is bounded by 7
+        new Random().nextBytes(array);
+        String generatedString = new String(array, Charset.forName("UTF-8"));
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingPlainJava_whenGeneratingRandomStringBounded_thenCorrect() {
+        int leftLimit = 97; // letter 'a'
+        int rightLimit = 122; // letter 'z'
+        int targetStringLength = 10;
+        Random random = new Random();
+        StringBuilder buffer = new StringBuilder(targetStringLength);
+
+        for (int i = 0; i < targetStringLength; i++) {
+            int randomLimitedInt = leftLimit + (int) (random.nextFloat() * (rightLimit - leftLimit + 1));
+            buffer.append((char) randomLimitedInt);
+        }
+        String generatedString = buffer.toString();
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingJava8_whenGeneratingRandomAlphabeticString_thenCorrect() {
+        int leftLimit = 97; // letter 'a'
+        int rightLimit = 122; // letter 'z'
+        int targetStringLength = 10;
+        Random random = new Random();
+
+        String generatedString = random.ints(leftLimit, rightLimit + 1)
+            .limit(targetStringLength)
+            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
+            .toString();
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingJava8_whenGeneratingRandomAlphanumericString_thenCorrect() {
+        int leftLimit = 48; // numeral '0'
+        int rightLimit = 122; // letter 'z'
+        int targetStringLength = 10;
+        Random random = new Random();
+
+        String generatedString = random.ints(leftLimit, rightLimit + 1)
+            .filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
+            .limit(targetStringLength)
+            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
+            .toString();
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomString_thenCorrect() {
+        String generatedString = RandomStringUtils.random(10);
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomAlphabeticString_thenCorrect() {
+        String generatedString = RandomStringUtils.randomAlphabetic(10);
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomAlphanumericString_thenCorrect() {
+        String generatedString = RandomStringUtils.randomAlphanumeric(10);
+
+        LOG.debug(generatedString);
+    }
+
+    @Test
+    public void givenUsingApache_whenGeneratingRandomStringBounded_thenCorrect() {
+        int length = 10;
+        boolean useLetters = true;
+        boolean useNumbers = false;
+        String generatedString = RandomStringUtils.random(length, useLetters, useNumbers);
+
+        LOG.debug(generatedString);
+    }
+
+}