字符串str =这是字符串文字"；

这是字符串文字.像这样声明字符串时，实际上是在String上调用intern()方法.此方法引用内部字符串对象池.如果已经存在一个字符串值"This is stringliteral"，则str将引用该字符串，并且不会创建新的String对象.

String str = "This is string literal";

This is string literal. When you declare string like this, you are actually calling intern() method on String. This method references internal pool of string objects. If there already exists a string value "This is string literal", then str will reference of that string and no new String object will be created.

这是字符串对象.在这种方法中，即使引用池中有这是由新操作员创建的字符串"，JVM也***创建新的字符串引用.

This is string object. In this method JVM is forced to create a new string reference, even if "this is string created by new operator" is in the reference pool.