public class first{public static void main(String args[]){    String asd = "helloworld";    String asf = "hello world love";    System.out.println(asd.contains("hello"));//判断“hello”是否存在    System.out.println(asd.indexOf("d",5));//从第5开始查找 d 的位置 返回他的索引找不到返回-1    System.out.println(asd.lastIndexOf("h",1));     System.out.println(asd.startsWith("ll",1));//从索引1开始查找 判断是否以ll开头     System.out.println(asd.replaceAll("o","-"));//把o替换成-    System.out.println(asd.substring(1,5));   String it [] = asf.split("\\ ");//拆分操作   for (int x=0;x<it.length ;x++ )   { System.out.println(it[x]);   }    }}