String Searching & Modifying - Java Questions & Answers

This section of our 1000+ Java MCQs focuses on searching and modifying a string of Java Programming Language.

1. Which of this method of class String is used to extract a substring from a String object?
a) substring()
b) Substring()
c) SubString()
d) None of the mentioned
View Answer

Answer: a
Explanation: The substring() method is a predefined method in the String class that returns a portion of the string based on the given arguments.

2. What will s2 contain after following lines of Java code?

 String s1 = "one";
String s2 = s1.concat("two")

a) one
b) two
c) onetwo
d) twoone
View Answer

Answer: c
Explanation: Two strings can be concatenated by using concat() method.

3. Which of these method of class String is used to remove leading and trailing whitespaces?
a) startsWith()
b) trim()
c) Trim()
d) doTrim()
View Answer

Answer: b
Explanation: The trim() method is a predefined method that removes leading and trailing whitespace characters such as newline (\n), tab (\t), and space ( ).

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4. What is the value returned by function compareTo() if the invoking string is greater than the string compared?
a) zero
b) value less than zero
c) value greater than zero
d) none of the mentioned
View Answer

Answer: c
Explanation: : compareTo() method returns the int value

-ve when comparing string is smaller than comparing string.
+ve when comparing string is greater than comparing string.
0 when comparing strings are equal.

5. Which of the following statement is correct?
a) replace() method replaces all occurrences of one character in invoking string with another character
b) replace() method replaces only first occurrences of a character in invoking string with another character
c) replace() method replaces all the characters in invoking string with another character
d) replace() replace() method replaces last occurrence of a character in invoking string with another character
View Answer

Answer: a
Explanation: replace() method replaces all occurrences of one character in invoking string with another character.

6. What will be the output of the following Java program?

```
    class output 
```
```
    {
```

        public static void main(String args[])

```
        { 
```

           String c = "  Hello World  ";

```
           String s = c.trim();
```

           System.out.println("\""+s+"\"");

```
        }
```
```
    }
```

a) “”Hello World””
b) “”Hello World”
c) “Hello World”
d) Hello world
View Answer

Answer: c
Explanation: trim() method is used to remove leading and trailing whitespaces in a string.
Output:

$ javac output.java
$ java output
"Hello World"

7. What will be the output of the following Java program?

```
    class output 
```
```
    {
```

        public static void main(String args[])

```
        { 
```
```
           String s1 = "one";
```
```
           String s2 = s1 + " two";
```
```
           System.out.println(s2);
```
```
        }
```
```
    }
```

a) one
b) two
c) one two
d) compilation error
View Answer

Answer: c
Explanation: The expression s1 + ” two” performs string concatenation, resulting in “one two”, which is assigned to s2. The System.out.println(s2); statement then prints “one two” to the console.
Output:

$ javac output.java
$ java output
one two

8. What will be the output of the following Java program?

```
    class output 
```
```
    {
```

        public static void main(String args[])

```
        { 
```
```
           String s1 = "Hello";
```

           String s2 = s1.replace('l','w');

```
           System.out.println(s2);
```
```
        }
```
```
    }
```

a) Hello
b) Helwo
c) Hewlo
d) Hewwo
View Answer

Answer: d
Explanation: replace() method replaces all occurrences of one character in invoking string with another character. s1.replace(‘l’,’w’) replaces every occurrence of ‘l’ in Hello by ‘w’, giving Hewwo.
Output:

$ javac output.java
$ java output
Hewwo

9. What will be the output of the following Java program?

```
    class output 
```
```
    {
```

        public static void main(String args[])

```
        {
```
```
           String s1 = "Hello World";
```

           String s2 = s1.substring(0 , 4);

```
           System.out.println(s2);
```
```
        }
```
```
   }
```

a) Hell
b) Hello
c) Worl
d) World
View Answer

Answer: a
Explanation: substring(0,4) returns the character from 0 th position to 3 rd position.
output:

$ javac output.java
$ java output 
Hell

10. What will be the output of the following Java program?

```
    class output 
```
```
    {
```

        public static void main(String args[])

        {             String s = "Hello World";

```
             int i = s.indexOf('o');
```

             int j = s.lastIndexOf('l');

             System.out.print(i + " " + j);

```
 
```
```
        }
```
```
   }
```

a) 4 8
b) 5 9
c) 4 9
d) 5 8
View Answer

Answer: c
Explanation: indexOf() method returns the index of first occurrence of the character where as lastIndexOf() returns the index of last occurrence of the character.
output:

$ javac output.java
$ java output  
4 9

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