请说说String的replace和replaceAll方法的区别？

replace方法：支持字符和字符串的替换。

public String replace(char oldChar, char newChar)
 
public String replace(CharSequence target, CharSequence replacement)

replaceAll方法：基于正则表达式的字符串替换。

public String replaceAll(String regex, String replacement)

测试代码：

String str = "Hello Java. Java is a language.";
System.out.println(str.replace("Java.", "c++"));//打印 Hello c++ Java is a language.
System.out.println(str.replaceAll("Java.", "c++"));//打印 Hello c++ c++is a language.

打印结果：

Hello c++ Java is a language.
Hello c++ c++is a language.