Please explain the function of these methods in Java?

Question

1. x&=3
2. x|=3
3. x<<=3
4. x>>=3

Explain:-
.indexOf()

Answer 1

• The indexOf() method is used to get the integer value of a particular index of String type object, based on criteria specified in the parameters of the indexOf() method.

• The indexOf(String target) method searches left-to-right inside the given string for a "target" string. The indexOf() method returns the index number where the target string is first found or -1 if the target is not found.

String s = "Here there everywhere";
int x = s.indexOf("there"); // x is 5
int y = s.indexOf("er"); // y is 1
int z = s.indexOf("eR"); // z is -1, "eR" is not found

• String indexOf() method example:
https://beginnersbook.com/2013/12/java-string-indexof-method-example/

Answer 2

For example
"Sololearn".indexOf("lo") returns 2

Answer 3

What about the operators from 1 to 4?

Answer 4

In the first answer, why z=-1?