Java Operators, Expressions and Scanner Input: ICSE Class 8 with Outputs

Understand Operators, Expressions and Input with Scanner in Java

import java.util.Scanner;
class Interest
{
    public static void main(String args[])
    {
        Scanner sc = new Scanner(System.in);
        double p = sc.nextDouble();
        double r = sc.nextDouble();
        double t = sc.nextDouble();
        double si = p * r * t / 100;
        System.out.println("Simple interest = " + si);
    }
}

Operators, Expressions and Input with Scanner in Java: key facts

Operator groups

Arithmetic	add, subtract, multiply, divide, remainder
Relational	greater, less, equal, not equal
Logical	AND, OR, NOT
Assignment	=

Relational and logical give true or false.

Integer division

• •Int divided by int drops the decimal
• •Remainder operator gives what is left
• •17 / 5 = 3
• •Remainder of 17 by 5 = 2
• •17.0 / 5 = 3.4

One decimal operand gives a decimal answer.

Scanner methods

nextInt	int
nextDouble	double
next	one word
nextLine	whole line

Import java.util.Scanner first.

How to answer Operators, Expressions and Input with Scanner in Java questions

1. 1Mark the data type of each operand.
2. 2Apply brackets, then * / %, then + -.
3. 3For int division keep only the whole part.
4. 4For text joining, work left to right and check where the text starts.
5. 5For Scanner programs, list the inputs in the order they are read.

Operators, Expressions and Input with Scanner in Java in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Tricks to remember Operators, Expressions and Input with Scanner in Java

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Slash shares, percent leftovers

  / gives the quotient, % the remainder for ints.

  Use it when: Division of integers.

• One equals assigns, two compare

  = assigns, == compares.

  Use it when: Common slip.

Operators, Expressions and Input with Scanner in Java: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

int x = 8;
x = x + 2;
x = x * 4;
System.out.println(x);
System.out.println(x > 30 && x <= 40);
System.out.println(!(x == 40));

Where students lose marks in Operators, Expressions and Input with Scanner in Java

The slips examiners see most often, and what to write instead.

• ✗Mistake: Expecting 3.4 from 17 / 5

  int division drops the decimal part.

  Wrong working

  17 / 5 = 3.4

  Right working

  17 / 5 = 3

  ✓Do this: Use 17.0 / 5 for 3.4.

  Usually costs: 1 mark

• ✗Mistake: Using = to compare

  Comparison uses ==.

  Wrong working

  if (a = b)

  Right working

  if (a == b)

  ✓Do this: Two equals for comparing.

  Usually costs: 1 mark

• ✗Mistake: Missing the import

  Scanner needs importing.

  Wrong working

  No import line.

  Right working

  import java.util.Scanner;

  ✓Do this: Write it at the top.

  Usually costs: 1 mark

Practice questions on Operators, Expressions and Input with Scanner in Java

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which operator gives the remainder?
   (a) / (b) * (c) % (d) &&

   Hint

   The percent sign.

   Answer

   (c) %.

2. Q2 · 2 marks · Short answerBoard level

   What is the value of 17.0 / 5 and why does it differ from 17 / 5? (2 marks)

   Hint

   A decimal operand.

   Answer

   17.0 / 5 is 3.4 because a decimal operand gives a decimal answer; 17 / 5 is 3 because int division drops the decimal part.

3. Q3 · 3 marks · Short answerHarder board level

   With a = 17 and b = 5 find: a > 10 && b > 10, a > 10 || b > 10 and !(a > b). (3 marks)

   Hint

   AND needs both.

   Answer

   false, true, false.

4. Q4 · 4 marks · Long answerHarder board level

   Write a Java program to read principal 5000, rate 8 and time 3 as doubles and print the simple interest and the amount, and give the output. (4 marks)

   Hint

   Use Scanner and nextDouble.

   Answer

   Read p, r and t with nextDouble. si = p * r * t / 100 = 1200.0; amt = p + si = 6200.0. Output: Simple interest = 1200.0 and Amount = 6200.0.

5. Q5 · 4 marks · Long answerHOTS / competency

   A student writes if (x = 5). Explain the mistake and the correct comparison, and state the type of error. (4 marks)

   Hint

   Assign versus compare.

   Answer

   The single = assigns 5 to x instead of comparing; the comparison is x == 5. Java reports this as a compile error because an if condition must be true or false and an assignment gives a number.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What does % give?Show answer

   The remainder.

2. 2.What does && mean?Show answer

   Logical AND.

3. 3.Which method reads a double?Show answer

   nextDouble.

4. 4.What does != mean?Show answer

   Not equal to.

5. 5.What does 17 / 5 give for ints?Show answer

   3.

6. 6.Which class reads keyboard input?Show answer

   Scanner.

Operators, Expressions and Input with Scanner in Java: frequently asked questions