net.dongliu.commons.lang.Strings Maven / Gradle / Ivy

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package net.dongliu.commons.lang;

import java.util.Collection;

/**
 * string utils methods
 *
 * @author Dong Liu
 */
public class Strings {

    /**
     * get sub string by begin(included) and end(not included) index.
     * begin and end can be negative, will be eval as str.length() + begin/end.
     *      *     sub("test", 1, 2) returns "e"
     *     sub("test", 1, -1) returns "es"
     *     sub("test", -2, -1) returns "s"
     *     sub(null, -2, -1) returns null
     * 
     *
     * @param str can be null. when str is null, always return null
     * @return subString
     * @throws ArrayIndexOutOfBoundsException
     */
    public static String sub(String str, int begin, int end) {
        if (str == null) {
            return null;
        }
        int len = str.length();
        if (begin < 0) {
            begin += len;
        }
        if (end < 0) {
            end += len;
        }
        if (begin >= len || begin < 0) {
            throw new ArrayIndexOutOfBoundsException("invalid start index:" + begin);
        }
        if (end > len || end < 0) {
            throw new ArrayIndexOutOfBoundsException("invalid end index:" + end);
        }
        return str.substring(begin, end);
    }

    /**
     * get sub string by begin(included) index, till the end of string.
     * begin can be negative, will be eval as str.length() + begin.
     *      *     sub("test", 1) returns "est"
     *     sub("test", -2) returns "st"
     *     sub(null, -2) returns null
     * 
     *
     * @param str can be null. when str is null, always return null
     * @return subString
     * @throws ArrayIndexOutOfBoundsException
     */
    public static String sub(String str, int begin) {
        if (str == null) {
            return null;
        }
        return str.substring(begin, str.length());
    }

    /**
     * get sub-string between begin and end.
     *
     * @param str   if null, return null
     * @param begin the begin str, cannot be null
     * @param end   the end str, cannot be null
     * @return str between begin and end. if not exists, return null
     */
    public static String between(String str, String begin, String end) {
        if (str == null) {
            return null;
        }

        int idx = str.indexOf(begin);
        if (idx < 0) {
            return null;
        }
        idx += begin.length();
        int eidx = str.indexOf(end, idx);
        if (eidx < 0) {
            return null;
        }
        return str.substring(idx, eidx);
    }

    /**
     * split str by white characters
     *      * "a   b c" --> ["a", "b", "c"]
     * " a c " --> ["a","c"]
     * 
     */
    public String[] split(String str) {
        return str.trim().split("\\w+");
    }

    /**
     * join str
     *      * join(",","b", "c") --> "b,c"
     * 
     *
     * @return string
     */
    public static String join(String separator, String... strings) {
        StringBuilder sb = new StringBuilder();
        int total = strings.length;
        int i = 0;
        for (String str : strings) {
            sb.append(str);
            if (i++ < total - 1) {
                sb.append(separator);
            }
        }
        return sb.toString();
    }


    /**
     * join strings with separator
     *
     * @param strings   not null
     * @param separator not null
     * @return string not null
     */
    public static String join(String separator, Collection strings) {
        StringBuilder sb = new StringBuilder();
        int total = strings.size();
        int i = 0;
        for (String str : strings) {
            sb.append(str);
            if (i++ < total - 1) {
                sb.append(separator);
            }
        }
        return sb.toString();
    }
}