var data: String? = null
        logD(TAG, "null 0 [${data.isNullOrBlank()}]") // output: null 0 [true]
        logD(TAG, "null 1 [${data.isNullOrEmpty()}]") // output: null 1 [true]
        logD(TAG, "null 2 [${data?.isBlank()}]")      // output: null 2 [null]
        logD(TAG, "null 3 [${data?.isEmpty()}]")      // output: null 3 [null]

        data = ""
        logD(TAG, "no space 0 [${data.isNullOrBlank()}]") // output: no space 0 [true]
        logD(TAG, "no space 1 [${data.isNullOrEmpty()}]") // output: no space 1 [true]
        logD(TAG, "no space 2 [${data.isBlank()}]")       // output: no space 2 [true]
        logD(TAG, "no space 3 [${data.isEmpty()}]")       // output: no space 3 [true]

        data = "hello"
        logD(TAG, "hello 0 [${data.isNullOrBlank()}]") // output: hello 0 [false]
        logD(TAG, "hello 1 [${data.isNullOrEmpty()}]") // output: hello 1 [false]
        logD(TAG, "hello 2 [${data.isBlank()}]")       // output: hello 2 [false]
        logD(TAG, "hello 3 [${data.isEmpty()}]")       // output: hello 3 [false]

        data = " " // this is a text with blank space
        logD(TAG, "blank space 0 [${data.isNullOrBlank()}]") // output: blank space 0 [true]
        logD(TAG, "blank space 1 [${data.isNullOrEmpty()}]") // output: blank space 1 [false]
        logD(TAG, "blank space 2 [${data.isBlank()}]")       // output: blank space 2 [true]
        logD(TAG, "blank space 3 [${data.isEmpty()}]")       // output: blank space 3 [false]
        
        logD(TAG, "blank space 4 [${data.isNotBlank()}]")    // output: blank space 4 [false]
        logD(TAG, "blank space 5 [${data.isNotEmpty()}]")    // output: blank space 5 [true]

總結：" "blank space isBlank=true isEmpty=false