Merge pull request #9045 from patkorek/BAEL-2660

BAEL-2660 few examples to convert String to Int

core-groovy/src/test/groovy/com/baeldung/stringtoint/ConvertStringToInt.groovy

@@ -0,0 +1,110 @@
+package com.baeldung.stringtoint
+
+import org.junit.Test
+
+import java.text.DecimalFormat
+
+import static org.junit.Assert.assertEquals
+import static org.junit.Assert.assertNull
+
+class ConvertStringToInt {
+
+    @Test
+    void givenString_whenUsingAsInteger_thenConvertToInteger() {
+        def stringNum = "123"
+        def invalidString = "123a"
+        Integer expectedInteger = 123
+        Integer integerNum = stringNum as Integer
+        def intNum = invalidString?.isInteger() ? invalidString as Integer : null
+
+        assertNull(null, intNum)
+        assertEquals(integerNum, expectedInteger)
+    }
+
+    @Test
+    void givenString_whenUsingAsInt_thenConvertToInt() {
+        def stringNum = "123"
+        int expectedInt = 123
+        int intNum = stringNum as int
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test
+    void givenString_whenUsingToInteger_thenConvertToInteger() {
+        def stringNum = "123"
+        int expectedInt = 123
+        int intNum = stringNum.toInteger()
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test
+    void givenString_whenUsingParseInt_thenConvertToInteger() {
+        def stringNum = "123"
+        int expectedInt = 123
+        int intNum = Integer.parseInt(stringNum)
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test
+    void givenString_whenUsingValueOf_thenConvertToInteger() {
+        def stringNum = "123"
+        int expectedInt = 123
+        int intNum = Integer.valueOf(stringNum)
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test
+    void givenString_whenUsingIntValue_thenConvertToInteger() {
+        def stringNum = "123"
+        int expectedInt = 123
+        int intNum = new Integer(stringNum).intValue()
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test
+    void givenString_whenUsingNewInteger_thenConvertToInteger() {
+        def stringNum = "123"
+        int expectedInt = 123
+        int intNum = new Integer(stringNum)
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test
+    void givenString_whenUsingDecimalFormat_thenConvertToInteger() {
+        def stringNum = "123"
+        int expectedInt = 123
+        DecimalFormat decimalFormat = new DecimalFormat("#")
+        int intNum = decimalFormat.parse(stringNum).intValue()
+
+        assertEquals(intNum, expectedInt)
+    }
+
+    @Test(expected = NumberFormatException.class)
+    void givenInvalidString_whenUsingAs_thenThrowNumberFormatException() {
+        def invalidString = "123a"
+        invalidString as Integer
+    }
+
+    @Test(expected = NullPointerException.class)
+    void givenNullString_whenUsingToInteger_thenThrowNullPointerException() {
+        def invalidString = null
+        invalidString.toInteger()
+    }
+
+    @Test
+    void givenString_whenUsingIsInteger_thenCheckIfCorrectValue() {
+        def invalidString = "123a"
+        def validString = "123"
+        def invalidNum = invalidString?.isInteger() ? invalidString as Integer : false
+        def correctNum = validString?.isInteger() ? validString as Integer : false
+
+        assertEquals(false, invalidNum)
+        assertEquals(123, correctNum)
+    }
+}