java 字符串处理的

@Test
    public void testString(){
        /*字符串处理   */
        String email="123456789@qq.com";
        System.out.println("字符串长度 "+email.length());
        System.out.println(email.indexOf("@"));
        System.out.println(email.substring(0, email.indexOf("@")));
        System.out.println(email.toLowerCase()+" "+email.toUpperCase());
        String[]arrayStr=email.split("@");
        for (String temp:arrayStr){
            System.out.println(temp);
        }
        /*==比较的是内存的地址 equals比较的是值 */
        String str1=new String("123");String str2=new String("123");
        System.out.println(str1==str2);
        System.out.println(str1.equals(str2));
        /*存的是常量值*/
        String str3="123";String str4="123";
        System.out.println(str3==str4);
        System.out.println(str3.equals(str4));

    }