How to convert String type to int type in java

In java, the methods to convert String type to int type are: Integer.parseInt (String) method, Integer.valueOf (String) method.

This article will introduce to you two methods of converting the String type to the int type in Java, so that you can understand how the String type can be converted to the int type. I hope it will be helpful to you.

1. Integer.parseInt(String) method

parseInt() is in the Integer wrapper class A method that can parse a string into a signed integer

Example: Define a String variable str with a value of "1234" and an integer variable inum with a value of 100. ; Use the parseInt() method, take the variable str as its parameter, and return the integer value to the int type variable inum2 after parsing; finally output the sum of the integer variables "inum" and "inum2" (the sum of the integer variable sum value).

package com.beginnersbook;
public class JavaExample{
   public static void main(String args[]){
	String str="123";
	int inum = 100;

	/* converting the string to an int value
	 * ,the value of inum2 would be 123 after
	 * conversion
	 */
	int inum2 = Integer.parseInt(str);
		
	int sum = inum+inum2;
	System.out.println("Result is: "+sum);
   }

Running result:

Note: When using the parseInt() method, all characters in the string must be numbers, but the One character can be the minus sign "-". Example:

String str="-1234";
int inum = Integer.parseInt(str);

In this way, the value of the converted variable inum will be: -1234;

If only part of all the characters in the string are numbers, then the conversion is invalid, Integer. parseInt() will throw an exception, prompt: NumberFormatException. Example:

String str="1122ab";
int num = Integer.valueOf(str);

This will throw NumberFormatException (number format exception). You will see compilation errors like this:

2, Integer.valueOf(String) method

valueOf() is also a method of the Integer wrapper class, which can convert a String type value into an int type value. This is similar to the parseInt() method, and their converted output results are the same.

However, there are still differences between Integer.valueOf() and Integer.parseInt():

The valueOf(String) method returns an object of the Integer class, while the parseInt(String) method Returns the original int value.

Example:

package com.beginnersbook;
public class JavaExample{
   public static void main(String args[]){
	//String with negative sign
	String str="-234";
		
	//An int variable
	int inum = 110;
		
	/* Convert String to int in Java using valueOf() method
	 * the value of variable inum2 would be negative after 
	 * conversion
	 */
	int inum2 = Integer.valueOf(str);
		
	//Adding up inum and inum2
	int sum = inum+inum2;
		
	//displaying sum
	System.out.println("Result is: "+sum);
   }}

Run result:

It can be seen that the valueOf(String) method is similar to the parseInt(String) method. Use When using this method, all characters in the string must be numbers, but the first character can be the minus sign "-"; and when not all characters in the String type are numbers, an exception will also be thrown: NumberFormatException.

Example: When String str="11aa22";, an exception will be thrown and NumberFormatException will be thrown.

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