Multiply two long integers, checking for overflow. : Long « Data Type « Java Tutorial





import java.io.File;

/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *
 */
public class Main {

  /**
   * Multiply two long integers, checking for overflow.
   * 
   * @param a first value
   * @param b second value
   * @return the product <code>a * b</code>
   * @throws ArithmeticException if the result can not be represented as an
   *         long
   * @since 1.2
   */
  public static long mulAndCheck(long a, long b) {
      long ret;
      String msg = "overflow: multiply";
      if (a > b) {
          // use symmetry to reduce boundry cases
          ret = mulAndCheck(b, a);
      } else {
          if (a < 0) {
              if (b < 0) {
                  // check for positive overflow with negative a, negative b
                  if (a >= Long.MAX_VALUE / b) {
                      ret = a * b;
                  } else {
                      throw new ArithmeticException(msg);
                  }
              } else if (b > 0) {
                  // check for negative overflow with negative a, positive b
                  if (Long.MIN_VALUE / b <= a) {
                      ret = a * b;
                  } else {
                      throw new ArithmeticException(msg);
                      
                  }
              } else {
                  // assert b == 0
                  ret = 0;
              }
          } else if (a > 0) {
              // assert a > 0
              // assert b > 0
              
              // check for positive overflow with positive a, positive b
              if (a <= Long.MAX_VALUE / b) {
                  ret = a * b;
              } else {
                  throw new ArithmeticException(msg);
              }
          } else {
              // assert a == 0
              ret = 0;
          }
      }
      return ret;
  }
}










2.8.Long
2.8.1.Long Integer Literal
2.8.2.Create a Long object
2.8.3.Add two long integers, checking for overflow.
2.8.4.Multiply two long integers, checking for overflow.
2.8.5.Subtract two long integers, checking for overflow.
2.8.6.Convert Long to numeric primitive data types example
2.8.7.Convert long primitive to Long object Example
2.8.8.Compute distance light travels using long variables
2.8.9.Java long Example: long is 64 bit signed type
2.8.10.Min and Max values of datatype long
2.8.11.Gets the maximum of three long values.
2.8.12.Gets the minimum of three long values.
2.8.13.Convert Java String to Long example
2.8.14.Use toString method of Long class to convert Long into String.
2.8.15.Convert from long to String
2.8.16.Convert from String to long
2.8.17.A utility class for converting a long into a human readable string.
2.8.18.Java Sort long Array Example
2.8.19.Compare Two Java long Arrays Example
2.8.20.Format long with System.out.format