How do I search a list in Java?

JavaObject Oriented ProgrammingProgramming

Streams can be used to search an item within list.

Student student2 = list.stream().filter(s -> {return s.getRollNo() == rollNo);}).findAny().orElse(null);

In this example, we're searching a student by roll number.

Example

Following is the example showing the usage of streams to search an item in a list −

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.List;

public class CollectionsDemo {
   public static void main(String[] args) {
      List<Student> list = new ArrayList<>();
      list.add(new Student(1, "Zara"));
      list.add(new Student(2, "Mahnaz"));
      list.add(new Student(3, "Ayan"));
      System.out.println("List: " + list);
      final int rollNoToSearch = 3;
      Student student = list.stream().filter(s -> {return s.getRollNo() == rollNoToSearch;}).findAny().orElse(null);
      System.out.println(student);
      final int rollNoToSearch1 = 4;
      student = list.stream().filter(s -> {return s.getRollNo() == rollNoToSearch1;}).findAny().orElse(null);
      System.out.println(student);
   }
}
class Student {
   private int rollNo;
   private String name;
   public Student(int rollNo, String name) {
      this.rollNo = rollNo;
      this.name = name;
   }
   public int getRollNo() {
      return rollNo;
   }
   public void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   @Override
   public boolean equals(Object obj) {
      if(!(obj instanceof Student)) {
         return false;
      }
      Student student = (Student)obj;
      return this.rollNo == student.getRollNo() && this.name.equals(student.getName());
   }
   @Override
   public String toString() {
      return "[" + this.rollNo + "," + this.name + "]";
   }
}

Output

This will produce the following result −

List: [[1,Zara], [2,Mahnaz], [3,Ayan]]
[3,Ayan]
null
raja
Updated on 09-May-2022 13:54:32

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