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2010-06-01T06:33:00Z

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в 18:01, 31 мая 2010

2010-05-31T18:01:44Z

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== Multiply two integers, checking for overflow. ==



<source lang="java">

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 integers, checking for overflow.
*
* @param x a factor
* @param y a factor
* @return the product <code>x*y</code>
* @throws ArithmeticException if the result can not be represented as an
* int
* @since 1.1
*/
public static int mulAndCheck(int x, int y) {
long m = ((long)x) * ((long)y);
if (m < Integer.MIN_VALUE || m > Integer.MAX_VALUE) {
throw new ArithmeticException("overflow: mul");
}
return (int)m;
}
}

</source>



== Multiply two long integers, checking for overflow. ==



<source lang="java">

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;
}
}

</source>



== Subtract two integers, checking for overflow. ==



<source lang="java">

import java.math.BigDecimal;
/*
* 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 {
/**
* Subtract two integers, checking for overflow.
*
* @param x the minuend
* @param y the subtrahend
* @return the difference <code>x-y</code>
* @throws ArithmeticException if the result can not be represented as an
* int
* @since 1.1
*/
public static int subAndCheck(int x, int y) {
long s = (long)x - (long)y;
if (s < Integer.MIN_VALUE || s > Integer.MAX_VALUE) {
throw new ArithmeticException("overflow: subtract");
}
return (int)s;
}
}

</source>



== Subtract two long integers, checking for overflow. ==



<source lang="java">

import java.math.BigDecimal;
/*
* 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 {
/**
* Subtract two long integers, checking for overflow.
*
* @param a first value
* @param b second value
* @return the difference <code>a-b</code>
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long subAndCheck(long a, long b) {
long ret;
String msg = "overflow: subtract";
if (b == Long.MIN_VALUE) {
if (a < 0) {
ret = a - b;
} else {
throw new ArithmeticException(msg);
}
} else {
// use additive inverse
ret = addAndCheck(a, -b, msg);
}
return ret;
}
/**
* Add two long integers, checking for overflow.
*
* @param a an addend
* @param b an addend
* @param msg the message to use for any thrown exception.
* @return the sum <code>a+b</code>
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
private static long addAndCheck(long a, long b, String msg) {
long ret;
if (a > b) {
// use symmetry to reduce boundry cases
ret = addAndCheck(b, a, msg);
} else {
// assert a <= b

if (a < 0) {
if (b < 0) {
// check for negative overflow
if (Long.MIN_VALUE - b <= a) {
ret = a + b;
} else {
throw new ArithmeticException(msg);
}
} else {
// oppisite sign addition is always safe
ret = a + b;
}
} else {
// assert a >= 0
// assert b >= 0
// check for positive overflow
if (a <= Long.MAX_VALUE - b) {
ret = a + b;
} else {
throw new ArithmeticException(msg);
}
}
}
return ret;
}
}

</source>

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Admin: 1 версия

в 18:01, 31 мая 2010