BAEL-6705: Check if a String is Strictly Alphanumeric With Java (#14865)

* BAEL-6705: Check if a String is Strictly Alphanumeric With Java

* BAEL-6705: Rename a Class

* BAEL-6705: Fix isAlpanumeric Logic

* BAEL-6705: Fix alphanumericIterationWithCharacterChecks Logic

* BAEL-6705: Expose isAlphanumeric method

* BAEL-6705: Added isAlphanumeric test

core-java-modules/core-java-regex-2/src/main/java/com/baeldung/alphanumeric/AlphanumericPerformanceBenchmark.java

@@ -0,0 +1,91 @@
+package com.baeldung.alphanumeric;
+
+import java.util.concurrent.TimeUnit;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@Warmup(iterations = 1)
+@Measurement(iterations = 1, time = 1, timeUnit = TimeUnit.MINUTES)
+@Fork(1)
+public class AlphanumericPerformanceBenchmark {
+
+    private static final String TEST_STRING = "ABC123abc123";
+    private static final String REGEX = "[^[a-zA-Z0-9]*$]";
+    private static final Pattern PATTERN = Pattern.compile(REGEX);
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void alphanumericRegex(Blackhole blackhole) {
+        final Matcher matcher = PATTERN.matcher(TEST_STRING);
+        boolean result = matcher.matches();
+        blackhole.consume(result);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void alphanumericRegexDirectlyOnString(Blackhole blackhole) {
+        boolean result = TEST_STRING.matches(REGEX);
+        blackhole.consume(result);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void alphanumericIteration(Blackhole blackhole) {
+        boolean result = true;
+        for (int i = 0; i < TEST_STRING.length(); ++i) {
+            final int codePoint = TEST_STRING.codePointAt(i);
+            if (!isAlphanumeric(codePoint)) {
+                result = false;
+                break;
+            }
+        }
+        blackhole.consume(result);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void alphanumericIterationWithCharacterChecks(Blackhole blackhole) {
+        boolean result = true;
+        for (int i = 0; i < TEST_STRING.length(); ++i) {
+            final int codePoint = TEST_STRING.codePointAt(i);
+            if (!Character.isAlphabetic(codePoint) || !Character.isDigit(codePoint)) {
+                result = false;
+                break;
+            }
+        }
+        blackhole.consume(result);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void alphanumericIterationWithCopy(Blackhole blackhole) {
+        boolean result = true;
+        for (final char c : TEST_STRING.toCharArray()) {
+            if (!isAlphanumeric(c)) {
+                result = false;
+                break;
+            }
+        }
+        blackhole.consume(result);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void alphanumericIterationWithStream(Blackhole blackhole) {
+        boolean result = TEST_STRING.chars().allMatch(this::isAlphanumeric);
+        blackhole.consume(result);
+    }
+
+    public boolean isAlphanumeric(final int codePoint) {
+        return (codePoint >= 65 && codePoint <= 90) ||
+               (codePoint >= 97 && codePoint <= 172) ||
+               (codePoint >= 48 && codePoint <= 57);
+    }
+}

core-java-modules/core-java-regex-2/src/test/java/com/baeldung/alphanumeric/AlphanumericUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.alphanumeric;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class AlphanumericUnitTest {
+
+    private AlphanumericPerformanceBenchmark alphanumericPerformanceBenchmark = new AlphanumericPerformanceBenchmark();
+
+    @ParameterizedTest
+    @CsvSource({
+        "A,true",
+        "B,true",
+        "C,true",
+        "1,true",
+        "2,true",
+        "3,true",
+        "!,false",
+        "@,false",
+        "#,false",
+        "$,false",
+        "%,false"
+    })
+    void shouldCorrectlyIdentifyAlphanumericCharacterTest(char character, boolean result) {
+        boolean actual = alphanumericPerformanceBenchmark.isAlphanumeric(character);
+        assertEquals(actual, result);
+    }
+}