Oracle Software Engineer Senior interview questions

What is synchronised How memory management is done in java, why heap and stack only used in java String immutability, why is it called. What happens when you store a variable What is System.out.print What are static variables and why used, static vs nonStatic ObjectClass functions like: toString() ..give examples and how are they implemented What is HashCode and equals What is singleTon design principle. Write code for it. How are you going to scale if more instances need to be added DSA: given (a,b) and (c,d) you can add b to a and a to b, such that a=c, b=d If this pair is possible return true, in recursion