com.google.devtools.build.xcode.util.Interspersing.java Source code

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Here is the source code for com.google.devtools.build.xcode.util.Interspersing.java

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// Copyright 2014 Google Inc. All rights reserved.
//
// 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.google.devtools.build.xcode.util;

import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

/**
 * Utility code for interspersing items into sequences.
 */
public class Interspersing {
    private Interspersing() {
    }

    /**
     * Inserts {@code what} before each item in {@code sequence}, returning a lazy sequence of twice
     * the length.
     */
    public static <E> Iterable<E> beforeEach(final E what, Iterable<E> sequence) {
        Preconditions.checkNotNull(what);
        return Iterables.concat(Iterables.transform(sequence, new Function<E, Iterable<E>>() {
            @Override
            public Iterable<E> apply(E element) {
                return ImmutableList.of(what, element);
            }
        }));
    }

    /**
     * Prepends {@code what} to each string in {@code sequence}, returning a lazy sequence of the 
     * same length.
     */
    public static Iterable<String> prependEach(final String what, Iterable<String> sequence) {
        Preconditions.checkNotNull(what);
        return Iterables.transform(sequence, new Function<String, String>() {
            @Override
            public String apply(String input) {
                return what + input;
            }
        });
    }

    /**
     * Similar to {@link #prependEach(String, Iterable)}, but also converts each item in the sequence
     * to a string.
     */
    public static <E> Iterable<String> prependEach(String what, Iterable<E> sequence,
            Function<? super E, String> toString) {
        return prependEach(what, Iterables.transform(sequence, toString));
    }
}