Add code examples for String to int mini-article

core-java-8/src/test/java/com/baeldung/StringToIntTest.java

@@ -0,0 +1,53 @@
+package com.baeldung;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringToIntTest {
+
+    @Test
+    public void givenString_shouldConvertToInt1() throws Exception {
+        String givenString = "42";
+
+        int result = Integer.parseInt(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+
+    @Test
+    public void givenString_shouldConvertToInt2() throws Exception {
+        String givenString = "42";
+
+        Integer result = Integer.valueOf(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+    @Test
+    public void givenString_shouldConvertToInt3() throws Exception {
+        String givenString = "42";
+
+        Integer result = new Integer(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+    @Test
+    public void givenString_shouldConvertToInt4() throws Exception {
+        String givenString = "42";
+
+        int result = Integer.decode(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenInvalidInput_shouldThrow() throws Exception {
+        String givenString = "nan";
+
+        int result = Integer.parseInt(givenString);
+    }
+
+}