kotlin入门-扩展

1.为现有类添加方法和属性

2.对现有类添加属性的时候不能直接赋值

--------------------------------------------kotlin代码-------------------------------------------------------------------

/**
 * 扩展String的方法
 */
fun String.multi(int: Int): String {
    val sb = StringBuilder()
    for (i in 0 until int) {
        sb.append(this)
    }
    return sb.toString()
}

/**
 * 扩展String方法重写操作符
 */
operator fun String.times(int: Int): String {
    val sb = StringBuilder()
    for (i in 0 until int) {
        sb.append(this)
    }
    return sb.toString()
}

/**
 * 扩展成员变量 必须要get方法
 */
val String.a: String
    get() = "aaa"

/**
 * 输出结果:
abcabcabcabcabcabcabcabcabcabc
abcdabcdabcdabcdabcdabcdabcdabcdabcdabcd
aaa
 */
fun main(args: Array<String>) {
    println("abc".multi(10))
    println("abcd" * 10)
    println("454".a)

}

--------------------------------------------java代码----------------------------------------------------------------------

public class ExtendJava {
    public static void main(String[] args) {
        /**
         * 输出结果=>abcabcabcabcabcabcabcabcabcabc
         * =>aaa
         */
        System.out.println(ExtendKt.times("abc", 10));
        System.out.println(ExtendKt.getA("345"));
    }
}