Move StringToInt examples

core-java/src/test/java/com/baeldung/StringToIntOrIntegerTest.java

@@ -0,0 +1,62 @@
+package com.baeldung;
+
+import com.google.common.primitives.Ints;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringToIntOrIntegerTest {
+
+    @Test
+    public void givenString_whenParsingInt_shouldConvertToInt() {
+        String givenString = "42";
+
+        int result = Integer.parseInt(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+
+    @Test
+    public void givenString_whenCallingIntegerValueOf_shouldConvertToInt() {
+        String givenString = "42";
+
+        Integer result = Integer.valueOf(givenString);
+
+        assertThat(result).isEqualTo(new Integer(42));
+    }
+
+    @Test
+    public void givenString_whenCallingIntegerConstructor_shouldConvertToInt() {
+        String givenString = "42";
+
+        Integer result = new Integer(givenString);
+
+        assertThat(result).isEqualTo(new Integer(42));
+    }
+
+    @Test
+    public void givenString_whenCallingIntegerDecode_shouldConvertToInt() {
+        String givenString = "42";
+
+        int result = Integer.decode(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+    @Test
+    public void givenString_whenTryParse_shouldConvertToInt() {
+        String givenString = "42";
+
+        Integer result = Ints.tryParse(givenString);
+
+        assertThat(result).isEqualTo(42);
+    }
+
+    @Test(expected = NumberFormatException.class)
+    public void givenInvalidInput_whenParsingInt_shouldThrow() {
+        String givenString = "nan";
+        Integer.parseInt(givenString);
+    }
+
+}