Fixed sonarcloud warnings.

Author: javadev

src/main/java/com/github/underscore/MemoizeFunction.java

@@ -9,9 +9,8 @@ public abstract class MemoizeFunction<F, T> implements Function<F, T> {
     public abstract T calc(final F n);
 
     public T apply(final F key) {
-        if (!cache.containsKey(key)) {
-            cache.put(key, calc(key));
-        }
-        return cache.get(key);
+        final T value = calc(key);
+        cache.putIfAbsent(key, value);
+        return value;
     }
 }

src/main/java/com/github/underscore/Optional.java

@@ -6,7 +6,7 @@
 import java.util.function.Supplier;
 
 public final class Optional<T> {
-    private static final Optional<?> EMPTY = new Optional();
+    private static final Optional<?> EMPTY = new Optional<>();
     private final T arg;
     private final boolean absent;
 
@@ -99,7 +99,7 @@ public boolean equals(final Object o) {
             return false;
         }
 
-        final Optional optional = (Optional) o;
+        final Optional<?> optional = (Optional) o;
 
         return absent == optional.absent && Objects.equals(arg, optional.arg);
     }

src/main/java/com/github/underscore/U.java

@@ -2892,8 +2892,7 @@ public Chain<T> tap(final Consumer<T> func) {
         }
 
         public Chain<T> forEach(final Consumer<T> func) {
-            U.each(list, func);
-            return new Chain<>(list);
+            return tap(func);
         }
 
         public Chain<T> forEachRight(final Consumer<T> func) {
@@ -3180,9 +3179,7 @@ public String join() {
     @SuppressWarnings("unchecked")
     public static <T> List<T> push(final List<T> list, final T ... values) {
         final List<T> result = newArrayList(list);
-        for (T value : values) {
-            result.add(value);
-        }
+        Collections.addAll(result, values);
         return result;
     }
 

src/main/java/com/github/underscore/lodash/Json.java

@@ -30,6 +30,7 @@
 
 public final class Json {
     private static final String NULL = "null";
+    private static final String DIGIT = "digit";
 
     public static class JsonStringBuilder {
         public enum Step {
@@ -689,7 +690,7 @@ private Number readNumber() {
             readChar('-');
             int firstDigit = current;
             if (!readDigit()) {
-                throw expected("digit");
+                throw expected(DIGIT);
             }
             if (firstDigit != '0') {
                 while (readDigit()) {
@@ -722,7 +723,7 @@ private boolean readFraction() {
                 return false;
             }
             if (!readDigit()) {
-                throw expected("digit");
+                throw expected(DIGIT);
             }
             while (readDigit()) {
             }
@@ -737,7 +738,7 @@ private boolean readExponent() {
                 readChar('-');
             }
             if (!readDigit()) {
-                throw expected("digit");
+                throw expected(DIGIT);
             }
             while (readDigit()) {
             }