Java String interview questions

Hi,

We can get below type of questions in interview for java strings.

public class StringExample {

    public static void main(String a[]) throws Exception {
            String s11 = "ABC";
            String s111 = "ABC";
            String s234 = new String("ABC");
            System.out.println(s11.equals(s111));
            System.out.println(s11==s111);
//below line prints false as new object will created for s234(hashcode will different for two objects)
            System.out.println(s11==s234);
//below line prints true as it will check for string value(ABC) not for object
            System.out.println(s11.equals(s234));
  }
}

What is the out put:

correct answer is
true
true
false
true

Java Constructor Interview Program

Hi ,

We can find below type of questions in interviews. Please write the out put for below program.

public class ConstructorExample1 {

    static int j;
    public ConstructorExample1() {
        System.out.println("default");
    }

    public ConstructorExample1(int i) {
        this();//It will call default constructor
        System.out.println("p1");
    }

    public ConstructorExample1(String i, int j) {
//        ConstructorExample1();
        this(j);//it will call current class constructor which has one integer as variable
        System.out.println("p2");
    }
   
    public static void getData(){
        j = 2*7;
        System.out.println(j);
    }
   
    public  void getData1(){
        j = 2*7;
        System.out.println(j);
    }
    public static void main(String a[]){
//        ConstructorExample1 constructorExample1 = new ConstructorExample1();
//        ConstructorExample1 constructorExample11 = new ConstructorExample1(1);
//Below line of code will print all constructor outputs
ConstructorExample1 constructorExample111 = new ConstructorExample1("bal", 2);
    }
}

Below are the options which we will get in exam: Correct answer is option d
a.) compilation error
b) default
    p1
c) runtime error
d) default
    p1
    p2
e) p2

Sorting List of Beans in Java

If we have list of beans and if we want to sort the list based on bean property, we can use the bellow code.

Collections.sort(beans, new Comparator() { 
@Override 
public int compare(SortingBean o1, SortingBean o2) {
          return o1.getName().compareTo(o1.getName()); 
} 
}); 

Example:

package com.sample.java.testing;

public class SortingBean {

    private int id;
    private String name;
    private String role;


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }
}
 
Sorting  code:

package com.sample.java.testing;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class BeanSortExample {

    public static void main(String[] args) {
        /**
         * Just as an example, creating the beans and added into the list. But
         * generally , we will get these results from database or from some other
         * source. Then if we need any sorting the list, then we can use below
         * code.
         */
        List<SortingBean> beans = new ArrayList<SortingBean>();
        SortingBean bean = new SortingBean();
        bean.setId(200);
        bean.setName("jklmn");
        bean.setRole("TA");
        SortingBean bean1 = new SortingBean();
        bean1.setId(101);
        bean1.setName("abcde");
        bean1.setRole("TA");
        SortingBean bean3 = new SortingBean();
        bean3.setId(203);
        bean3.setName("zxyv");
        bean3.setRole("TA");
        beans.add(bean);
        beans.add(bean1);
        beans.add(bean3);
        System.out.println("before sort....");
        for (SortingBean unSortingBean : beans) {
            System.out.println("list of employee ids... " + unSortingBean.getId());
        }
        /**
         * Below lines of code will sort the list of beans based on the id property.
         */
        Collections.sort(beans, new Comparator<SortingBean>() {

            @Override
            public int compare(SortingBean o1, SortingBean o2) {
               return Integer.compare(o1.getId(), o2.getId());
            }
        });
        System.out.println("after sort....");
        for (SortingBean sortingBean : beans) {
            System.out.println("list of employee ids... " + sortingBean.getId());
        }
    }
}