The difference between java equals and ==

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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