jdk11新特性

有夢想一起實作

1.String

1.重複String.repeat(int)

var name = "zhangsan";
System.out.println(name.repeat(3));
           

輸出結果zhangsan*3

zhangsanzhangsanzhangsan
           

2.判斷目前字元串是否為空字元串（不包括空格和null的判斷）String.isEmpty（）

var emptyValue = "";
System.out.println(emptyValue.isEmpty());
           

輸出結果true

3.判斷字元串是否為"“或者” "String.isBlank()

String blank = " ";
String blank2 = "";
System.out.println("blank:" + blank.isBlank() + "blank2:" + blank2.isBlank());
           

輸出結果true

4.去除字元串前後空格String.strip()去掉首尾空格，String.stripLeading()去掉首空格，String.stripTrailing()去掉尾部空格

var strip = " 空格 空格 ";
System.out.println(
                  "strip:[" + strip.strip() + "]"
                   + "stripLeadind:[" + strip.stripLeading() + "]"
                   + "stripTrailing:[" + strip.stripTrailing() + "]"
        );

//輸出結果
strip:[空格 空格]stripLeadind:[空格 空格 ]stripTrailing:[ 空格 空格]        
           

2.Collection

1.List.of()改屬性為不可改變的 - - - 該屬性jdk9就有的

var strings = List.of("one", "two", "three");
System.out.println("strings:[" + strings + "]");
//輸出結果 strings:[[one, two, three]]
           

2.List.toArray() 将List轉換成String[ ]相當于list.toArray(new String[list.size()])

var list = List.of("one", "two", "three");
String[] strings = list.toArray(String[]::new);
System.out.println("strings:[" + Arrays.toString(strings) + "]");
//輸出結果 strings:[[one, two, three]]
           

3.Files.writeString()和Files.readString()

//将string寫入檔案
 Files.writeString(Path.of("./", "test.txt"), "hello work");
//将檔案内容傳回string格式
var readString = Files.readString(Path.of("./", "test.txt"));
System.out.println("readString:" + readString);
           

4.HttpClient後面單獨出一篇文章因為這個在實際項目中也是用的比較多的