java Do While循环终止，不执行scanner函数

Question

下面是我的“Do While”循环代码。在do{}部分末尾输入变量“redo”的值之前，我都搞不懂它为什么会终止。它在打印“您想再做一次吗”部分后立即终止

import java.util.Scanner;
public class AlgWorkbench0402 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        String redo;

        do {
            System.out.println("Enter in two integers and get the sum.");
            int val1, val2;
            val1 = Integer.valueOf(scanner.nextInt());
            val2 = Integer.valueOf(scanner.nextInt());

            System.out.println(val1 + val2);
            System.out.println("Would you like to do this again? [y/n]");

            redo = scanner.nextLine();

        }
        while (redo == "y" || redo == "Y");
    }
}