java String

public static void main(String[] args) { String str1 = "aaa"; String str2 = "aaa"; String str3 = new String("aaa"); String str4 = str1+""; String str5 = "aa"+"a"; System.out.println(str1 == str3); System.out.println(str1.equals(str3)); System.out.println(str1==str2); System.out.println(str1 == str4); System.out.println(str3 == str4); System.out.println(str1 == str5); /** * String 相加 ==> str4 = str1+""; */ /* String str1 = "aaa"; StringBuilder sb = new StringBuilder(); sb.append(str1).append(""); String str4 = sb.toString(); */ }

结果：

false

true

true

false

false

true

所以有大量“+”的拼接操作时用StringBuilder 或者StringBuffer会省下很多内存;

StringBuilder和StringBuffer作用类似,只是StringBuffer的由于增加了同步锁是线程安全的，但是会稍微影响性能;