first commit

java/expression/Reverse.java

@@ -0,0 +1,84 @@
+package expression;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.List;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class Reverse extends AbstractExpression {
+
+    private final AbstractExpression operand;
+
+    public Reverse(AbstractExpression operand) {
+        this.operand = operand;
+    }
+
+    private static int reverseInt(int n) {
+        boolean negative = n < 0;
+        long abs = Math.abs((long) n);
+        long reversed = 0;
+        while (abs > 0) {
+            reversed = reversed * 10 + (abs % 10);
+            abs /= 10;
+        }
+        long result = negative ? -reversed : reversed;
+        return (int) result;
+    }
+
+    @Override
+    public int evaluate(int x) {
+        return reverseInt(operand.evaluate(x));
+    }
+
+    @Override
+    public int evaluate(int x, int y, int z) {
+        return reverseInt(operand.evaluate(x, y, z));
+    }
+
+    @Override
+    public int evaluate(List<Integer> vars) {
+        return reverseInt(operand.evaluate(vars));
+    }
+
+    @Override
+    public BigInteger evaluateBi(List<BigInteger> vars) {
+        throw new UnsupportedOperationException(
+            "reverse not supported for BigInteger"
+        );
+    }
+
+    @Override
+    public BigDecimal evaluateBd(List<BigDecimal> vars) {
+        throw new UnsupportedOperationException(
+            "reverse not supported for BigDecimal"
+        );
+    }
+
+    @Override
+    public String toString() {
+        return "reverse(" + operand + ")";
+    }
+
+    @Override
+    public String toMiniString() {
+        if (operand instanceof AbstractBinaryOperation) {
+            return "reverse(" + operand.toMiniString() + ")";
+        }
+
+        return "reverse " + operand.toMiniString();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) return true;
+        if (!(obj instanceof Reverse)) return false;
+        return operand.equals(((Reverse) obj).operand);
+    }
+
+    @Override
+    public int hashCode() {
+        return operand.hashCode() ^ 0x52455645;
+    }
+}