2020-10-29 Update: Added "Parse nice int from char problem" and "Is valid identifier?"

Author: fartem

src/main/java/com/smlnskgmail/jaman/codewarsjava/kyu7/IsValidIdentifier.java

@@ -0,0 +1,18 @@
+package com.smlnskgmail.jaman.codewarsjava.kyu7;
+
+// https://www.codewars.com/kata/563a8656d52a79f06c00001f
+public class IsValidIdentifier {
+
+    private final String input;
+
+    public IsValidIdentifier(String input) {
+        this.input = input;
+    }
+
+    public boolean solution() {
+        return input.length() > 1
+                && input.substring(0, 1).matches("^[a-zA-Z_$]*$")
+                && input.substring(1).matches("^[a-zA-Z0-9_$]*$");
+    }
+
+}

src/main/java/com/smlnskgmail/jaman/codewarsjava/kyu8/ParseNiceIntFromCharProblem.java

@@ -0,0 +1,16 @@
+package com.smlnskgmail.jaman.codewarsjava.kyu8;
+
+// https://www.codewars.com/kata/557cd6882bfa3c8a9f0000c1
+public class ParseNiceIntFromCharProblem {
+
+    private final String input;
+
+    public ParseNiceIntFromCharProblem(String input) {
+        this.input = input;
+    }
+
+    public int solution() {
+        return Character.getNumericValue(input.charAt(0));
+    }
+
+}

src/test/java/com/smlnskgmail/jaman/codewarsjava/kyu7/IsValidIdentifierTest.java

@@ -0,0 +1,20 @@
+package com.smlnskgmail.jaman.codewarsjava.kyu7;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class IsValidIdentifierTest {
+
+    @Test
+    public void testValid() {
+        assertTrue(new IsValidIdentifier("i1").solution());
+    }
+
+    @Test
+    public void testInvalid() {
+        assertFalse(new IsValidIdentifier("1i").solution());
+    }
+
+}

src/test/java/com/smlnskgmail/jaman/codewarsjava/kyu8/ParseNiceIntFromCharProblemTest.java

@@ -0,0 +1,33 @@
+package com.smlnskgmail.jaman.codewarsjava.kyu8;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class ParseNiceIntFromCharProblemTest {
+
+    @Test
+    public void test1() {
+        assertEquals(
+                5,
+                new ParseNiceIntFromCharProblem("5 years old").solution()
+        );
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(
+                9,
+                new ParseNiceIntFromCharProblem("9 years old").solution()
+        );
+    }
+
+    @Test
+    public void test3() {
+        assertEquals(
+                1,
+                new ParseNiceIntFromCharProblem("1 year old").solution()
+        );
+    }
+
+}