Returns the scheme prefix like "http" from the URL spec, or null if the spec doesn't start with a scheme. - Android Network

Android examples for Network:HTTP

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Description

Returns the scheme prefix like "http" from the URL spec, or null if the spec doesn't start with a scheme.

Demo Code

/*//from   ww w .java2s. c  o  m
 * Copyright (C) 2011 The Android Open Source Project
 *
 * 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.java2s;
import java.util.Locale;

public class Main {
    /**
     * Returns the scheme prefix like "http" from the URL spec, or null if the
     * spec doesn't start with a scheme. Scheme prefixes match this pattern:
     * {@code alpha ( alpha | digit | '+' | '-' | '.' )* ':'}
     */
    public static String getSchemePrefix(String spec) {
        int colon = spec.indexOf(':');

        if (colon < 1) {
            return null;
        }

        for (int i = 0; i < colon; i++) {
            char c = spec.charAt(i);
            if (!isValidSchemeChar(i, c)) {
                return null;
            }
        }

        return spec.substring(0, colon).toLowerCase(Locale.US);
    }

    public static boolean isValidSchemeChar(int index, char c) {
        if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
            return true;
        }
        if (index > 0
                && ((c >= '0' && c <= '9') || c == '+' || c == '-' || c == '.')) {
            return true;
        }
        return false;
    }
}

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