com.abubusoft.kripton.common.Preconditions Maven / Gradle / Ivy
/*******************************************************************************
* Copyright 2016-2019 Francesco Benincasa ([email protected])
*
* Licensed 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.
******************************************************************************/
package com.abubusoft.kripton.common;
// TODO: Auto-generated Javadoc
/**
* Static convenience methods that help a method or constructor check whether it was invoked correctly (whether its preconditions have been met). These methods generally
* accept a {@code boolean} expression which is expected to be {@code true} (or in the case of {@code checkNotNull}, an object reference which is expected to be non-null). When
* {@code false} (or {@code null}) is passed instead, the {@code Preconditions} method throws an unchecked exception, which helps the calling method communicate to its
* caller that that caller has made a mistake. Example:
*
*
* public static double sqrt(double value) {
* Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
* // calculate the square root
* }
*
* void exampleBadCaller() {
* double d = sqrt(-1.0);
* }}
*
*
* In this example, {@code checkArgument} throws an {@code IllegalArgumentException} to indicate that {@code exampleBadCaller} made an error in its call to {@code sqrt}.
*
* Warning about performance
*
*
* The goal of this class is to improve readability of code, but in some circumstances this may come at a significant performance cost. Remember that parameter values for message
* construction must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even when the precondition check then succeeds (as it should almost
* always do in production). In some circumstances these wasted CPU cycles and allocations can add up to a real problem. Performance-sensitive precondition checks can always be
* converted to the customary form:
*
*
* {@code
*
* if (value < 0.0) {
* throw new IllegalArgumentException("negative value: " + value);
* }}
*
*
* Other types of preconditions
*
*
* Not every type of precondition failure is supported by these methods. Continue to throw standard JDK exceptions such as {@link java.util.NoSuchElementException} or
* {@link UnsupportedOperationException} in the situations they are intended for.
*
*
Non-preconditions
*
*
* It is of course possible to use the methods of this class to check for invalid conditions which are not the caller's fault. Doing so is not recommended because it
* is misleading to future readers of the code and of stack traces. See Conditional failures
* explained in the Guava User Guide for more advice.
*
*
{@code java.util.Objects.requireNonNull()}
*
*
* Projects which use {@code com.google.common} should generally avoid the use of {@link java.util.Objects#requireNonNull(Object)}. Instead, use whichever of
* checkNotNull(Object) or Verify#verifyNotNull(Object) is appropriate to the situation. (The same goes for the message-accepting overloads.)
*
*
Only {@code %s} is supported
*
*
* In {@code Preconditions} error message template strings, only the {@code "%s"} specifier is supported, not the full range of {@link java.util.Formatter} specifiers.
*
*
More information
*
*
* See the Guava User Guide on using {@code Preconditions}.
*
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
public final class Preconditions {
/**
* Instantiates a new preconditions.
*/
private Preconditions() {
}
/**
* Ensures the truth of an expression involving one or more parameters to the calling method.
*
* @param expression
* a boolean expression
* @throws IllegalArgumentException
* if {@code expression} is false
*/
public static void checkArgument(boolean expression) {
if (!expression) {
throw new IllegalArgumentException();
}
}
/**
* Ensures the truth of an expression involving one or more parameters to the calling method.
*
* @param expression
* a boolean expression
* @param errorMessage
* the exception message to use if the check fails; will be converted to a string using {@link String#valueOf(Object)}
* @throws IllegalArgumentException
* if {@code expression} is false
*/
public static void checkArgument(boolean expression, Object errorMessage) {
if (!expression) {
throw new IllegalArgumentException(String.valueOf(errorMessage));
}
}
/**
* Ensures the truth of an expression involving one or more parameters to the calling method.
*
* @param expression
* a boolean expression
* @param errorMessageTemplate
* a template for the exception message should the check fail. The message is formed by replacing each {@code %s} placeholder in the template with an argument. These
* are matched by position - the first {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in square
* braces. Unmatched placeholders will be left as-is.
* @param errorMessageArgs
* the arguments to be substituted into the message template. Arguments are converted to strings using {@link String#valueOf(Object)}.
* @throws IllegalArgumentException
* if {@code expression} is false
* @throws NullPointerException
* if the check fails and either {@code errorMessageTemplate} or {@code errorMessageArgs} is null (don't let this happen)
*/
public static void checkArgument(boolean expression, String errorMessageTemplate, Object... errorMessageArgs) {
if (!expression) {
throw new IllegalArgumentException(format(errorMessageTemplate, errorMessageArgs));
}
}
/**
* Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
*
* @param expression
* a boolean expression
* @throws IllegalStateException
* if {@code expression} is false
*/
public static void checkState(boolean expression) {
if (!expression) {
throw new IllegalStateException();
}
}
/**
* Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
*
* @param expression
* a boolean expression
* @param errorMessage
* the exception message to use if the check fails; will be converted to a string using {@link String#valueOf(Object)}
* @throws IllegalStateException
* if {@code expression} is false
*/
public static void checkState(boolean expression, Object errorMessage) {
if (!expression) {
throw new IllegalStateException(String.valueOf(errorMessage));
}
}
/**
* Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
*
* @param expression
* a boolean expression
* @param errorMessageTemplate
* a template for the exception message should the check fail. The message is formed by replacing each {@code %s} placeholder in the template with an argument. These
* are matched by position - the first {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in square
* braces. Unmatched placeholders will be left as-is.
* @param errorMessageArgs
* the arguments to be substituted into the message template. Arguments are converted to strings using {@link String#valueOf(Object)}.
* @throws IllegalStateException
* if {@code expression} is false
* @throws NullPointerException
* if the check fails and either {@code errorMessageTemplate} or {@code errorMessageArgs} is null (don't let this happen)
*/
public static void checkState(boolean expression, String errorMessageTemplate, Object... errorMessageArgs) {
if (!expression) {
throw new IllegalStateException(format(errorMessageTemplate, errorMessageArgs));
}
}
/**
* Ensures that an object reference passed as a parameter to the calling method is not null.
*
* @param the generic type
* @param reference an object reference
* @return the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
*/
public static T checkNotNull(T reference) {
if (reference == null) {
throw new NullPointerException();
}
return reference;
}
/**
* Ensures that an object reference passed as a parameter to the calling method is not null.
*
* @param the generic type
* @param reference an object reference
* @param errorMessage the exception message to use if the check fails; will be converted to a string using {@link String#valueOf(Object)}
* @return the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
*/
public static T checkNotNull(T reference, Object errorMessage) {
if (reference == null) {
throw new NullPointerException(String.valueOf(errorMessage));
}
return reference;
}
/**
* Ensures that an object reference passed as a parameter to the calling method is not null.
*
* @param the generic type
* @param reference an object reference
* @param errorMessageTemplate a template for the exception message should the check fail. The message is formed by replacing each {@code %s} placeholder in the template with an argument. These
* are matched by position - the first {@code %s} gets {@code errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in square
* braces. Unmatched placeholders will be left as-is.
* @param errorMessageArgs the arguments to be substituted into the message template. Arguments are converted to strings using {@link String#valueOf(Object)}.
* @return the non-null reference that was validated
* @throws NullPointerException if {@code reference} is null
*/
public static T checkNotNull(T reference, String errorMessageTemplate, Object... errorMessageArgs) {
if (reference == null) {
// If either of these parameters is null, the right thing happens anyway
throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
}
return reference;
}
/*
* All recent hotspots (as of 2009) *really* like to have the natural code
*
* if (guardExpression) { throw new BadException(messageExpression); }
*
* refactored so that messageExpression is moved to a separate String-returning method.
*
* if (guardExpression) { throw new BadException(badMsg(...)); }
*
* The alternative natural refactorings into void or Exception-returning methods are much slower. This is a big deal - we're talking factors of 2-8 in microbenchmarks, not just
* 10-20%. (This is a hotspot optimizer bug, which should be fixed, but that's a separate, big project).
*
* The coding pattern above is heavily used in java.util, e.g. in ArrayList. There is a RangeCheckMicroBenchmark in the JDK that was used to test this.
*
* But the methods in this class want to throw different exceptions, depending on the args, so it appears that this pattern is not directly applicable. But we can use the
* ridiculous, devious trick of throwing an exception in the middle of the construction of another exception. Hotspot is fine with that.
*/
/**
* Ensures that {@code index} specifies a valid element in an array, list or string of size {@code size}. An element index may range from zero, inclusive, to
* {@code size}, exclusive.
*
* @param index
* a user-supplied index identifying an element of an array, list or string
* @param size
* the size of that array, list or string
* @return the value of {@code index}
* @throws IndexOutOfBoundsException
* if {@code index} is negative or is not less than {@code size}
* @throws IllegalArgumentException
* if {@code size} is negative
*/
public static int checkElementIndex(int index, int size) {
return checkElementIndex(index, size, "index");
}
/**
* Ensures that {@code index} specifies a valid element in an array, list or string of size {@code size}. An element index may range from zero, inclusive, to
* {@code size}, exclusive.
*
* @param index
* a user-supplied index identifying an element of an array, list or string
* @param size
* the size of that array, list or string
* @param desc
* the text to use to describe this index in an error message
* @return the value of {@code index}
* @throws IndexOutOfBoundsException
* if {@code index} is negative or is not less than {@code size}
* @throws IllegalArgumentException
* if {@code size} is negative
*/
public static int checkElementIndex(int index, int size, String desc) {
// Carefully optimized for execution by hotspot (explanatory comment above)
if (index < 0 || index >= size) {
throw new IndexOutOfBoundsException(badElementIndex(index, size, desc));
}
return index;
}
/**
* Bad element index.
*
* @param index the index
* @param size the size
* @param desc the desc
* @return the string
*/
private static String badElementIndex(int index, int size, String desc) {
if (index < 0) {
return format("%s (%s) must not be negative", desc, index);
} else if (size < 0) {
throw new IllegalArgumentException("negative size: " + size);
} else { // index >= size
return format("%s (%s) must be less than size (%s)", desc, index, size);
}
}
/**
* Ensures that {@code index} specifies a valid position in an array, list or string of size {@code size}. A position index may range from zero to {@code size},
* inclusive.
*
* @param index
* a user-supplied index identifying a position in an array, list or string
* @param size
* the size of that array, list or string
* @return the value of {@code index}
* @throws IndexOutOfBoundsException
* if {@code index} is negative or is greater than {@code size}
* @throws IllegalArgumentException
* if {@code size} is negative
*/
public static int checkPositionIndex(int index, int size) {
return checkPositionIndex(index, size, "index");
}
/**
* Ensures that {@code index} specifies a valid position in an array, list or string of size {@code size}. A position index may range from zero to {@code size},
* inclusive.
*
* @param index
* a user-supplied index identifying a position in an array, list or string
* @param size
* the size of that array, list or string
* @param desc
* the text to use to describe this index in an error message
* @return the value of {@code index}
* @throws IndexOutOfBoundsException
* if {@code index} is negative or is greater than {@code size}
* @throws IllegalArgumentException
* if {@code size} is negative
*/
public static int checkPositionIndex(int index, int size, String desc) {
// Carefully optimized for execution by hotspot (explanatory comment above)
if (index < 0 || index > size) {
throw new IndexOutOfBoundsException(badPositionIndex(index, size, desc));
}
return index;
}
/**
* Bad position index.
*
* @param index the index
* @param size the size
* @param desc the desc
* @return the string
*/
private static String badPositionIndex(int index, int size, String desc) {
if (index < 0) {
return format("%s (%s) must not be negative", desc, index);
} else if (size < 0) {
throw new IllegalArgumentException("negative size: " + size);
} else { // index > size
return format("%s (%s) must not be greater than size (%s)", desc, index, size);
}
}
/**
* Ensures that {@code start} and {@code end} specify a valid positions in an array, list or string of size {@code size}, and are in order. A position index may range
* from zero to {@code size}, inclusive.
*
* @param start
* a user-supplied index identifying a starting position in an array, list or string
* @param end
* a user-supplied index identifying a ending position in an array, list or string
* @param size
* the size of that array, list or string
* @throws IndexOutOfBoundsException
* if either index is negative or is greater than {@code size}, or if {@code end} is less than {@code start}
* @throws IllegalArgumentException
* if {@code size} is negative
*/
public static void checkPositionIndexes(int start, int end, int size) {
// Carefully optimized for execution by hotspot (explanatory comment above)
if (start < 0 || end < start || end > size) {
throw new IndexOutOfBoundsException(badPositionIndexes(start, end, size));
}
}
/**
* Bad position indexes.
*
* @param start the start
* @param end the end
* @param size the size
* @return the string
*/
private static String badPositionIndexes(int start, int end, int size) {
if (start < 0 || start > size) {
return badPositionIndex(start, size, "start index");
}
if (end < 0 || end > size) {
return badPositionIndex(end, size, "end index");
}
// end < start
return format("end index (%s) must not be less than start index (%s)", end, start);
}
/**
* Substitutes each {@code %s} in {@code template} with an argument. These are matched by position: the first {@code %s} gets {@code args[0]}, etc. If there are more arguments
* than placeholders, the unmatched arguments will be appended to the end of the formatted message in square braces.
*
* @param template a non-null string containing 0 or more {@code %s} placeholders.
* @param args the arguments to be substituted into the message template. Arguments are converted to strings using {@link String#valueOf(Object)}. Arguments can be null.
* @return the string
*/
// Note that this is somewhat-improperly used from Verify.java as well.
static String format(String template, Object... args) {
template = String.valueOf(template); // null -> "null"
// start substituting the arguments into the '%s' placeholders
StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
int templateStart = 0;
int i = 0;
while (i < args.length) {
int placeholderStart = template.indexOf("%s", templateStart);
if (placeholderStart == -1) {
break;
}
builder.append(template.substring(templateStart, placeholderStart));
builder.append(args[i++]);
templateStart = placeholderStart + 2;
}
builder.append(template.substring(templateStart));
// if we run out of placeholders, append the extra args in square braces
if (i < args.length) {
builder.append(" [");
builder.append(args[i++]);
while (i < args.length) {
builder.append(", ");
builder.append(args[i++]);
}
builder.append(']');
}
return builder.toString();
}
}