BAEL-1739 - Check If a String is Numeric in Java (#4209)

* BAEL-1725 Java Pass-by-reference vs Pass-by-value - First commit

* updated test cases

* First commit consisting only of test cases

* First commit with test cases

* Introduced JMH Michrobenchmarking

* Minor corrections

core-java/src/main/java/com/baeldung/stringisnumeric/Benchmarking.java

@@ -0,0 +1,75 @@
+package com.baeldung.stringisnumeric;
+
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+
+public class Benchmarking {
+    public static void main(String[] args) throws RunnerException {
+        Options opt = new OptionsBuilder()
+                .include(Benchmarking.class.getSimpleName())
+                .forks(1)
+                .build();
+
+        new Runner(opt).run();
+    }
+
+    @State(Scope.Thread)
+    public static class ExecutionPlan {
+        public String number = Integer.toString(Integer.MAX_VALUE);
+        public boolean isNumber = false;
+        public IsNumeric isNumeric= new IsNumeric();
+    }
+    
+    @Benchmark 
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public void usingCoreJava(ExecutionPlan plan) {
+        plan.isNumber = plan.isNumeric.usingCoreJava(plan.number);
+    }
+    
+    @Benchmark 
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public void usingRegularExpressions(ExecutionPlan plan) {
+        plan.isNumber = plan.isNumeric.usingRegularExpressions(plan.number);
+    }
+    
+    @Benchmark 
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public void usingNumberUtils_isCreatable(ExecutionPlan plan) {
+        plan.isNumber = plan.isNumeric.usingNumberUtils_isCreatable(plan.number);
+    }
+    
+    @Benchmark 
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public void usingNumberUtils_isParsable(ExecutionPlan plan) {
+        plan.isNumber = plan.isNumeric.usingNumberUtils_isParsable(plan.number);
+    }
+    
+    @Benchmark 
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public void usingStringUtils_isNumeric(ExecutionPlan plan) {
+        plan.isNumber = plan.isNumeric.usingStringUtils_isNumeric(plan.number);
+    }
+    
+    @Benchmark 
+    @BenchmarkMode(Mode.AverageTime)
+    @OutputTimeUnit(TimeUnit.NANOSECONDS)
+    public void usingStringUtils_isNumericSpace(ExecutionPlan plan) {
+        plan.isNumber = plan.isNumeric.usingStringUtils_isNumericSpace(plan.number);
+    }
+}

core-java/src/main/java/com/baeldung/stringisnumeric/IsNumeric.java

@@ -0,0 +1,35 @@
+package com.baeldung.stringisnumeric;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang3.math.NumberUtils;
+
+public class IsNumeric {
+    public boolean usingCoreJava(String strNum) {
+        try {
+            double d = Double.parseDouble(strNum);
+        } catch (NumberFormatException | NullPointerException nfe) {
+            return false;
+        }
+        return true;
+    }
+    
+    public boolean usingRegularExpressions(String strNum) {
+        return strNum.matches("-?\\d+(\\.\\d+)?");
+    }
+    
+    public boolean usingNumberUtils_isCreatable(String strNum) {
+        return NumberUtils.isCreatable(strNum);
+    }
+    
+    public boolean usingNumberUtils_isParsable(String strNum) {
+        return NumberUtils.isParsable(strNum);
+    }
+    
+    public boolean usingStringUtils_isNumeric(String strNum) {
+        return StringUtils.isNumeric(strNum);
+    }
+    
+    public boolean usingStringUtils_isNumericSpace(String strNum) {
+        return StringUtils.isNumericSpace(strNum);
+    }
+}

core-java/src/main/java/com/baeldung/stringisnumeric/IsNumericDriver.java

@@ -0,0 +1,33 @@
+package com.baeldung.stringisnumeric;
+
+import static com.baeldung.designpatterns.util.LogerUtil.LOG;
+
+public class IsNumericDriver {
+    private static IsNumeric isNumeric;
+    
+    static {
+        isNumeric =new IsNumeric();
+    }
+    
+    public static void main(String[] args) {
+        LOG.info("Testing all methods...");
+        
+        boolean res = isNumeric.usingCoreJava("1001");
+        LOG.info("Using Core Java : " + res);
+        
+        res = isNumeric.usingRegularExpressions("1001");
+        LOG.info("Using Regular Expressions : " + res);
+        
+        res =isNumeric.usingNumberUtils_isCreatable("1001");
+        LOG.info("Using NumberUtils.isCreatable : " + res);
+        
+        res =isNumeric.usingNumberUtils_isParsable("1001");
+        LOG.info("Using NumberUtils.isParsable : " + res);
+        
+        res =isNumeric.usingStringUtils_isNumeric("1001");
+        LOG.info("Using StringUtils.isNumeric : " + res);
+        
+        res =isNumeric.usingStringUtils_isNumericSpace("1001");
+        LOG.info("Using StringUtils.isNumericSpace : " + res);
+    }
+}

core-java/src/test/java/com/baeldung/stringisnumeric/CoreJavaIsNumericUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.stringisnumeric;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class CoreJavaIsNumericUnitTest {
+    public static boolean isNumeric(String strNum) {
+        try {
+            double d = Double.parseDouble(strNum);
+        } catch (NumberFormatException | NullPointerException nfe) {
+            return false;
+        }
+        return true;
+    }
+    
+    @Test
+    public void whenUsingCoreJava_thenTrue() {
+        // Valid Numbers
+        assertThat(isNumeric("22")).isTrue();
+        assertThat(isNumeric("5.05")).isTrue();
+        assertThat(isNumeric("-200")).isTrue(); 
+        assertThat(isNumeric("10.0d")).isTrue();
+        assertThat(isNumeric("   22   ")).isTrue();
+         
+        // Invalid Numbers
+        assertThat(isNumeric(null)).isFalse();
+        assertThat(isNumeric("")).isFalse();
+        assertThat(isNumeric("abc")).isFalse();
+    }
+}

core-java/src/test/java/com/baeldung/stringisnumeric/NumberUtilsIsCreatableUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.stringisnumeric;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.apache.commons.lang3.math.NumberUtils;
+import org.junit.Test;
+
+public class NumberUtilsIsCreatableUnitTest {
+    @Test
+    public void givenApacheCommons_whenUsingIsParsable_thenTrue() {
+        // Valid Numbers
+        assertThat(NumberUtils.isCreatable("22")).isTrue();
+        assertThat(NumberUtils.isCreatable("5.05")).isTrue();
+        assertThat(NumberUtils.isCreatable("-200")).isTrue();
+        assertThat(NumberUtils.isCreatable("10.0d")).isTrue();
+        assertThat(NumberUtils.isCreatable("1000L")).isTrue();
+        assertThat(NumberUtils.isCreatable("0xFF")).isTrue();
+        assertThat(NumberUtils.isCreatable("07")).isTrue();
+        assertThat(NumberUtils.isCreatable("2.99e+8")).isTrue();
+         
+        // Invalid Numbers
+        assertThat(NumberUtils.isCreatable(null)).isFalse();
+        assertThat(NumberUtils.isCreatable("")).isFalse();
+        assertThat(NumberUtils.isCreatable("abc")).isFalse();
+        assertThat(NumberUtils.isCreatable(" 22 ")).isFalse();
+        assertThat(NumberUtils.isCreatable("09")).isFalse();
+    }
+}

core-java/src/test/java/com/baeldung/stringisnumeric/NumberUtilsIsParsableUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.stringisnumeric;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.apache.commons.lang3.math.NumberUtils;
+import org.junit.Test;
+
+public class NumberUtilsIsParsableUnitTest {
+    @Test
+    public void givenApacheCommons_whenUsingIsParsable_thenTrue() {
+        // Valid Numbers
+        assertThat(NumberUtils.isParsable("22")).isTrue();
+        assertThat(NumberUtils.isParsable("-23")).isTrue();
+        assertThat(NumberUtils.isParsable("2.2")).isTrue();
+        assertThat(NumberUtils.isParsable("09")).isTrue();
+        
+        // Invalid Numbers
+        assertThat(NumberUtils.isParsable(null)).isFalse();
+        assertThat(NumberUtils.isParsable("")).isFalse();
+        assertThat(NumberUtils.isParsable("6.2f")).isFalse();
+        assertThat(NumberUtils.isParsable("9.8d")).isFalse();
+        assertThat(NumberUtils.isParsable("22L")).isFalse();
+        assertThat(NumberUtils.isParsable("0xFF")).isFalse();
+        assertThat(NumberUtils.isParsable("2.99e+8")).isFalse();
+    }
+}

core-java/src/test/java/com/baeldung/stringisnumeric/RegularExpressionsUnitTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.stringisnumeric;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class RegularExpressionsUnitTest {
+    public static boolean isNumeric(String strNum) {
+        return strNum.matches("-?\\d+(\\.\\d+)?");
+    }
+    
+    @Test
+    public void whenUsingRegularExpressions_thenTrue() {
+        // Valid Numbers
+        assertThat(isNumeric("22")).isTrue();
+        assertThat(isNumeric("5.05")).isTrue();
+        assertThat(isNumeric("-200")).isTrue();
+         
+        // Invalid Numbers
+        assertThat(isNumeric("abc")).isFalse();
+    }
+}

core-java/src/test/java/com/baeldung/stringisnumeric/StringUtilsIsNumericSpaceUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.stringisnumeric;
+
+import org.apache.commons.lang3.StringUtils;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringUtilsIsNumericSpaceUnitTest {
+    @Test
+    public void givenApacheCommons_whenUsingIsNumericSpace_thenTrue() {
+        // Valid Numbers
+        assertThat(StringUtils.isNumericSpace("123")).isTrue();
+        assertThat(StringUtils.isNumericSpace("١٢٣")).isTrue();
+        assertThat(StringUtils.isNumericSpace("")).isTrue();
+        assertThat(StringUtils.isNumericSpace("  ")).isTrue();
+        assertThat(StringUtils.isNumericSpace("12 3")).isTrue();
+         
+        // Invalid Numbers
+        assertThat(StringUtils.isNumericSpace(null)).isFalse();
+        assertThat(StringUtils.isNumericSpace("ab2c")).isFalse();
+        assertThat(StringUtils.isNumericSpace("12.3")).isFalse();
+        assertThat(StringUtils.isNumericSpace("-123")).isFalse();
+    }
+}

core-java/src/test/java/com/baeldung/stringisnumeric/StringUtilsIsNumericUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.stringisnumeric;
+
+import org.apache.commons.lang3.StringUtils;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringUtilsIsNumericUnitTest {
+    @Test
+    public void givenApacheCommons_whenUsingIsNumeric_thenTrue() {
+        // Valid Numbers
+        assertThat(StringUtils.isNumeric("123")).isTrue();
+        assertThat(StringUtils.isNumeric("١٢٣")).isTrue();
+        assertThat(StringUtils.isNumeric("१२३")).isTrue();
+         
+        // Invalid Numbers
+        assertThat(StringUtils.isNumeric(null)).isFalse();
+        assertThat(StringUtils.isNumeric("")).isFalse();
+        assertThat(StringUtils.isNumeric("  ")).isFalse();
+        assertThat(StringUtils.isNumeric("12 3")).isFalse();
+        assertThat(StringUtils.isNumeric("ab2c")).isFalse();
+        assertThat(StringUtils.isNumeric("12.3")).isFalse();
+        assertThat(StringUtils.isNumeric("-123")).isFalse();
+    }
+}