java9 example code:(Recommended learning:java course)
String str1 = "abc"; String str2 = "abc"; String str3 = new String("abc"); String str4 = new String("abc");
当： str1 == str2 输出：true 当：str1.equals(str2); 输出：true 当： str1 == str3 输出：false 当：str1.equals(str3); 输出：true 当： str3 == str4 输出：false 当：str3.equals(str4); 输出：true
Details involved:
- You can use the intern method in String. The string object has a reference to the string that is equal to it in the constant pool.
str3.intern() == str4.intern() 输出：true str1.intern().equals(str2.intern()) 输出：true str1.intern() == str1 输出：false - String str = new String("abc");创建了几个对象？
First of all, check whether there is "abc" in the constant pool. This string, if it exists (String str = "abc"; when it appears), creates one, if not, creates two (one in the constant pool, one in the heap).
The difference between equals and ==
For ==:
Acts on variables of basic data types , then directly compare whether the stored "values" are equal;
acts on reference type variables, then the comparison is the address of the object pointed to;
For equals:
The equals method cannot be applied to variables of basic data types;
If there is no equals method in Object If rewritten, the comparison is the address of the object pointed to by the reference type variable, otherwise the content is compared
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