Question

Java中的 Validate.isTrue(args.length == 1, "usage: supply url to fetch"); Validate是什么意思？

为什么我在网上没搜到？？？

Answer 1

第三方jar包commons-lang中的类
定义：
/**
* <p>Validate that the argument condition is {@code true}; otherwise
* throwing an exception with the specified message. This method is useful when
* validating according to an arbitrary boolean expression, such as validating a
* primitive number or using your own custom validation expression.</p>
*
* <pre>
* Validate.isTrue(i >= min && i <= max, "The value must be between %d and %d", min, max);
* Validate.isTrue(myObject.isOk(), "The object is not okay");</pre>
*
* @param expression the boolean expression to check
* @param message the {@link String#format(String, Object...)} exception message if invalid, not null
* @param values the optional values for the formatted exception message, null array not recommended
* @throws IllegalArgumentException if expression is {@code false}
* @see #isTrue(boolean)
* @see #isTrue(boolean, String, long)
* @see #isTrue(boolean, String, double)
*/
public static void isTrue(final boolean expression, final String message, final Object... values) {
if (expression == false) {
throw new IllegalArgumentException(String.format(message, values));
}
}

Answer 2

就是一个普通的类，可能是类似这样的定义：
public class Validate{
...

public static void isTrue(boolean condition, String message){

if(!condition){

throw new Exception(message);

}
}

...

}