java String intern_java

在周志明的《深入理解java虚拟机》，2nd，p57中有一部分代码

String str1 = new StringBuilder("计算机").append("软件").toString();
System.out.println(str1.intern() == str1);

String str2 = new StringBuilder("ja").append("va").toString();
System.out.println(str2.intern() == str2);

对照着intern()看了api源码上的javadoc注释

/**
 * Returns a canonical representation for the string object.
 * 
 * A pool of strings, initially empty, is maintained privately by the
 * class {@code String}.
 * 

 * When the intern method is invoked, if the pool already contains a
 * string equal to this {@code String} object as determined by
 * the {@link #equals(Object)} method, then the string from the pool is
 * returned. Otherwise, this {@code String} object is added to the
 * pool and a reference to this {@code String} object is returned.
 * 

 * It follows that for any two strings {@code s} and {@code t},
 * {@code s.intern() == t.intern()} is {@code true}
 * if and only if {@code s.equals(t)} is {@code true}.
 * 
 * All literal strings and string-valued constant expressions are
 * interned. String literals are defined in section 3.10.5 of the
 * The Java™ Language Specification.
 *
 * @return  a string that has the same contents as this string, but is
 *          guaranteed to be from a pool of unique strings.
 */
public native String intern();

个人理解是：