Java 中各种空（""、\u0000、null）的区别？

Question

String s1 = "";
String s2 = "\u0000";
String s3 = null;

s1、s2、s3 的区别，分别在字符串常量池和栈中的储存情况？

Answer 1

Let’s understand it from the perspective of class bytecode
1.String s1 = "", the following is the compiled bytecode, you can see that there is actually no difference in this case s1="aaa", they are all Push a string from the constant pool to the top of the stack and assign it to a local variable.

0: ldc           #16                 // String
2: astore_1
3: return

2. In the case of String s2=null, at this time, no string constant is generated in the constant pool, only null is pushed to the top of the stack and assigned to the variable.

0: aconst_null
1: astore_1
2: return

3. In the case of String s3 = "u0000", a string representing NUL will be generated in the constant pool, which is the so-called Control Character.

0: ldc           #16                 // String NUL
2: astore_1
3: return

Answer 2

Test environment: jdk-8.0-102