DoubleFunction.java

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package java.util.function;

/**
 * Represents a function that accepts a double-valued argument and produces a
 * result.  This is the {@code double}-consuming primitive specialization for
 * {@link Function}.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #apply(double)}.
 *
 * @param <R> the type of the result of the function
 *
 * @see Function
 * @since 1.8
 */
/*
 * 函数式接口：DoubleFunction<R>
 *
 * 参数：double
 * 返回：R
 * 示例：将double型数据d转换为字符串
 * DoubleFunction<String> f = d->Double.toString(d);
 */
@FunctionalInterface
public interface DoubleFunction<R> {
    
    /**
     * Applies this function to the given argument.
     *
     * @param value the function argument
     *
     * @return the function result
     */
    R apply(double value);
}