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Kotlin Standard Library for JVM

There is a newer version: 2.1.0-Beta1

package kotlin

import java.util.ArrayList
import java.util.HashMap
import java.util.HashSet
import java.util.LinkedList

/** Returns the string with leading and trailing text matching the given string removed */
public fun String.trim(text: String) : String = trimLeading(text).trimTrailing(text)

/** Returns the string with the prefix and postfix text trimmed */
public fun String.trim(prefix: String, postfix: String) : String = trimLeading(prefix).trimTrailing(postfix)

/** Returns the string with the leading prefix of this string removed */
public fun String.trimLeading(prefix: String): String {
    var answer = this
    if (answer.startsWith(prefix)) {
        answer = answer.substring(prefix.length())
    }
    return answer
}

/** Returns the string with the trailing postfix of this string removed */
public fun String.trimTrailing(postfix: String): String {
    var answer = this
    if (answer.endsWith(postfix)) {
        answer = answer.substring(0, length() - postfix.length())
    }
    return answer
}

/** Returns true if the string is not null and not empty */
public fun String?.isNotEmpty() : Boolean = this != null && this.length() > 0

/**
Iterator for characters of given CharSequence
*/
public fun CharSequence.iterator() : CharIterator = object : CharIterator() {
    private var index = 0

    public override fun nextChar(): Char = get(index++)

    public override fun hasNext(): Boolean = index < length
}

/** Returns the string if it is not null or the empty string if its null */
public fun String?.orEmpty(): String = this ?: ""


// "Extension functions" for CharSequence

val CharSequence.size : Int
get() = this.length

/**
 * Counts the number of characters which match the given predicate
 *
 * @includeFunctionBody ../../test/StringTest.kt count
 */
public inline fun String.count(predicate: (Char) -> Boolean): Int {
    var answer = 0
    for (c in this) {
        if (predicate(c)) {
            answer++
        }
    }
    return answer
}