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Java Stack peek() Method

The Java Stack peek() method is used to look at the object at the top of this stack without removing it from the stack.

Following is the declaration for java.util.Stack.peek() method.

public Object peek()

NA

The method call returns the object at the top of this stack.

EmptyStackException − This is thrown if this stack is empty.

The following example shows the usage of Java Stack peek() method to get the element from the top of the stack without removing it from the stack. In this example, we've created a Stack object of Integers. Then we've added few integers to the stack and printed the top element using peek() method.

package com.tutorialspoint;

import java.util.Stack;

public class StackDemo {
   public static void main(String args[]) {

      // creating stack
      Stack<Integer> st = new Stack<>();

      // populating stack
      st.push(10);
      st.push(20);
      st.push(30);

      // checking the top object
      System.out.println("Top object is: "+st.peek());
   }     
}

Let us compile and run the above program, this will produce the following result.

Top object is: 30

The following example shows the usage of Java Stack peek() method to get the String from the top of the stack without removing it from the stack. In this example, we've created a Stack object of Strings. Then we've added few strings to the stack and printed the top element using peek() method.

package com.tutorialspoint;

import java.util.Stack;

public class StackDemo {
   public static void main(String args[]) {

      // creating stack
      Stack<String> st = new Stack<>();

      // populating stack
      st.push("Java");
      st.push("Source");
      st.push("code");

      // checking the top object
      System.out.println("Top object is: "+st.peek());
   }     
}

Let us compile and run the above program, this will produce the following result.

Top object is: code

The following example shows the usage of Java Stack peek() method to get the student object from the top of the stack without removing it from the stack. In this example, we've created a Stack object of Student objects. Then we've added few student objects to the stack and printed the top element using peek() method.

package com.tutorialspoint;

import java.util.Stack;

public class StackDemo {
   public static void main(String args[]) {

      // creating stack
      Stack<Student> st = new Stack<>();

      // populating stack
      st.push(new Student(1, "Julie"));
      st.push(new Student(2, "Robert"));
      st.push(new Student(3, "Adam"));

      // checking the top object
      System.out.println("Top object is: "+st.peek());
   }     
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Let us compile and run the above program, this will produce the following result.

Top object is: [ 3, Adam ]

java_util_stack.htm

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