first commit

java/expression/exceptions/CheckedMultiply.java

@@ -0,0 +1,32 @@
+package expression.exceptions;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+
+import expression.*;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class CheckedMultiply extends AbstractBinaryOperation {
+    public CheckedMultiply(AbstractExpression l, AbstractExpression r) { super(l, r); }
+
+    @Override protected String  getOperator()  { return "*"; }
+    @Override protected int     getPriority()  { return 2; }
+    @Override protected boolean isRightAssoc() { return false; }
+
+    @Override
+    protected int applyInt(int a, int b) {
+        if (a == 0 || b == 0) return 0;
+        if (a == Integer.MIN_VALUE && b == -1) throw new OverflowException("multiplication");
+        if (b == Integer.MIN_VALUE && a == -1) throw new OverflowException("multiplication");
+        int result = a * b;
+        if (result / a != b) {
+            throw new OverflowException("multiplication");
+        }
+        return result;
+    }
+
+    @Override protected BigInteger applyBi(BigInteger a, BigInteger b) { return a.multiply(b); }
+    @Override protected BigDecimal applyBd(BigDecimal a, BigDecimal b) { return a.multiply(b); }
+}