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 these 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: None.

2. What will s2 contain after following lines of 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: None.

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:

 if (s1 == s2) then 0, if(s1 &gt; s2) &gt; 0, if (s1 &lt; s2) then &lt; 0.

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 is the output of this 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 is the output of this 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: None.
Output:

$ javac output.java
$ java output
one two

8. What is the output of this 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 is the output of this 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 is the output of this 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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