Arraylist java максимальное значение

Class ArrayList

Type Parameters: E — the type of elements in this list All Implemented Interfaces: Serializable , Cloneable , Iterable , Collection , List , RandomAccess Direct Known Subclasses: AttributeList , RoleList , RoleUnresolvedList

Resizable-array implementation of the List interface. Implements all optional list operations, and permits all elements, including null . In addition to implementing the List interface, this class provides methods to manipulate the size of the array that is used internally to store the list. (This class is roughly equivalent to Vector , except that it is unsynchronized.)

The size , isEmpty , get , set , iterator , and listIterator operations run in constant time. The add operation runs in amortized constant time, that is, adding n elements requires O(n) time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared to that for the LinkedList implementation.

Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at least as large as the list size. As elements are added to an ArrayList, its capacity grows automatically. The details of the growth policy are not specified beyond the fact that adding an element has constant amortized time cost.

An application can increase the capacity of an ArrayList instance before adding a large number of elements using the ensureCapacity operation. This may reduce the amount of incremental reallocation.

Note that this implementation is not synchronized. If multiple threads access an ArrayList instance concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements, or explicitly resizes the backing array; merely setting the value of an element is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be «wrapped» using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

List list = Collections.synchronizedList(new ArrayList(. ));

The iterators returned by this class’s iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator’s own remove or add methods, the iterator will throw a ConcurrentModificationException . Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

This class is a member of the Java Collections Framework.

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How To Find Maximum Value from ArrayList in Java — Collections.max()

A example program to find the maximum element from ArrayList. This is implemented in Java and finding max value. Finding max salary from Employee List with Collections.max().

1. Introduction

In this article, We’ll learn how to find the maximum (max) value from ArrayList. Finding the max value from ArrayList from Collection API is done by running a loop over all the elements or can be found max value with the Collections.max() method.

Collections.max(): Returns the maximum element of the given collection, according to the natural ordering of its elements.

Example programs to find the max value from a list of wrapper objects and a list of custom or user-defined objects.

2. Finding the max integer value from ArrayList

Create a list of integer values and pass the list to Collections.max(list). max() method sort the list of values in the natural order and return max value from it.

package com.java.w3schools.blog.arraylist; import java.util.ArrayList; import java.util.Collections; import java.util.List; /** * * Finding max value from list. * * @author javaprogramto.com * */ public class ArrayListMaxValue < public static void main(String[] args) < // creating list. ListintValues = new ArrayList<>(); // adding values intValues.add(6); intValues.add(64); intValues.add(45); intValues.add(60); intValues.add(9); intValues.add(2); // calling max() method. Integer max = Collections.max(intValues); System.out.println("ArrayList values : " + intValues); System.out.println("ArrayList max value : " + max); > >

ArrayList values : [6, 64, 45, 60, 9, 2] ArrayList max value : 64

3. Custom Objects — Find Max Salary Employee from list of Employee Objects

• First create an employee class with id, age and salary fields.
• Next, create a list of employee objects.
• Last, Call Collections.sort(listOfEmps) method that should return the Employee object with max salary.

package com.java.w3schools.blog.arraylist; import java.util.ArrayList; import java.util.Collections; import java.util.List; /** * * Find employee object with max salary. * * @author javaprogramto.com * */ public class ArrayListCustomObjectMaxValue < public static void main(String[] args) < // creating list with type Employee. ListempOfList = new ArrayList<>(); // adding values empOfList.add(new Employee(100, 45, 250000)); empOfList.add(new Employee(109, 38, 15000)); empOfList.add(new Employee(108, 23, 330000)); empOfList.add(new Employee(111, 55, 873983)); empOfList.add(new Employee(103, 25, 908022)); empOfList.add(new Employee(102, 35, 87272)); // calling max() method. Employee max = Collections.max(empOfList); System.out.println("ArrayList max value : " + max.getSalary() + " for emp id : " + max.getId()); > > class Employee implements Comparable  < private int id; private int age; private long salary; public Employee(int id, int age, long salary) < super(); this.id = id; this.age = age; this.salary = salary; >public int getId() < return id; >public int getAge() < return age; >public long getSalary() < return salary; >@Override public int compareTo(Employee o) < if (this.getSalary() >o.getSalary()) < return 1; >else if (this.getSalary() < o.getSalary()) < return -1; >return 0; > >

ArrayList max value : 908022 for emp id : 103

4. Exceptions with Collections.sort()

If the Employee class did not implement a Comparable interface then you will get compile time error as below.

Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method max(Collection) in the type Collections is not applicable for the arguments (List) at com.java.w3schools.blog.arraylist.ArrayListCustomObjectMaxValue.main(ArrayListCustomObjectMaxValue.java:30)

If the list is having other that Employee Objects then it will throw ClassCastException.

If the list is empty then you will get NoSuchElementException.

5. Conclusion

In this article, we’ve seen how to find the max element from the list. Examples are shown for wrapper objects and custom objects in the list to find the max value.

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A example program to find the maximum element from ArrayList. This is implemented in Java and finding max value. Finding max salary from Employee List with Collections.max().

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Find Minimum Maximum value in ArrayList

Find Minimum Maximum value in ArrayList Java example shows how to find the minimum and maximum value in ArrayList. The example also shows how to find minimum maximum value along with index in Java ArrayList.

How to find the Minimum Maximum value in ArrayList?

There are a couple of ways to find minimum and maximum value in Java ArrayList.

1) Find Min Max value in ArrayList using Collections class

You can use min and max methods of Collections class.

This method returns the minimum element/value of the specified collection according to the natural ordering of the elements.

This method returns the maximum element/value of the specified collection according to the natural ordering of the elements.

How to find an index of minimum maximum elements in Java ArrayList?

If you want to find index of minimum or maximum element instead of value, you can use indexOf method of the ArrayList class.

This method returns the index of the specified element. If the element is not found in the ArrayList, it returns -1.

2) Find Min Max value in ArrayList using for loop

If you want to find min max values without using the Collections class, you can use for loop to find the same as given below.

Please let me know your views in the comments section below.

About the author

I have a master’s degree in computer science and over 18 years of experience designing and developing Java applications. I have worked with many fortune 500 companies as an eCommerce Architect. Follow me on LinkedIn and Facebook.

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2 comments

What if there are duplicate entries in the ArrayList.. like 5 times number 1 ? This code will find only the first occurrence of number 1 and will say that’s the minimum as its the only one.. How to find all the minimum indexes.

Hello Simon, Even if the ArrayList has duplicates, the minimum value above code finds remains the same. So if ArrayList has 5 times 1, the minimum value is still 1 regardless of the index and that was the purpose of the above code, to find the minimum value. However, if you want to find index of all the minimum elements, that can be easily done by changing the code a little bit. Once you get the minimum element, scan through the ArrayList and check what all indexes has the element. I hope this answers your question. Thanks.

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