package com.aaa.zuoye;

 public class ZuoYe {

     public static void main(String[] args) {

         fun7();

     }

 //    (7)String trim(): 去掉字符串两端空格

     public static void fun7(){

         String str="       helloword    ";

         str=str.trim();

         System.out.println(str);

     }

 //    (6)String repalce(String old, String newstr): 将字符串中的老字符串,替换为新字符串

     public static void fun6(){

          String str="hellohaini";

          str=str.replaceFirst("h", "1");

          System.out.println(str);

     }

 //    (5)String repalce(char oldChar, char newChar): 将字符串中的老字符,替换为新字符

     public static void fun5(){

         String str="hello";

         str=str.replace("o", "a");

         System.out.println(str);

     }

 //    (4)String toUpperCase(): 字符串转成大写

     public static void fun4(){

         String str="hellO";

         System.out.println(str.toUpperCase());

     }

 //    (3)String toLowerCase(): 字符串转成小写

     public static void fun3(){

         String str1="helloWord";

         System.out.println(str1.toLowerCase());

     }

 //    (2)char charAt(int index): 返回索引上的字符

     public static void fun2(){

         String str1="helloWord";

         System.out.println(str1.charAt(2));

     }

     //(1)boolean isEmpty(): 判断字符串是不是空串,如果是空的就返回true

     public static boolean fun1(){

         String str1="";

         if(str1.isEmpty()==true){

             return true;

         }

         return false;

     }

 }