Write a java program that takes an expression in postfix notation as input and display the result after evaluating this expression.the expression is : 4 5 6 * +

Can you help me to do this Java program please? Thank you!

Write a program to compute the sum of the first N Fibonacci numbers, where N is an integer that is input by the user.  Once it computes the sum, the program will prompt the user for a new value of N.  The program will exit if the user enters a non-integer number or string (such as “quit”) instead of an integer.  Language: Java The first four numbers of the Fibonacci sequence are: 0, 1, 1, and 2. Use For loop at least once, can use while loops. Sample Output: Welcome to the Fibonacci AdderTo quit, enter a non-integer number or string How many Fibonacci numbers should be summed? >> 10The sum of the first 10 Fibonacci numbers is: 88 How many Fibonacci numbers should be summed? >> xxx Thank You for Using the Fibonacci Adder

Write in Java code

In Java:  Forms often allow a user to enter an integer. Write a program that takes in a string representing an integer as input, and outputs yes if every character is a digit 0-9. Ex: If the input is: 1995 the output is: yes Ex: If the input is: 42,000 or 1995! the output is: no Hint: Use a loop and the Character.isDigit() function.