## Java introduction lesson 94 -- parseInt method of integer

Monkeys learn to program 2020-11-13 02:42:12
java introduction lesson parseint method

## problem

test Integer Of parseInt Method , namely , First, string "123" Convert to int Type and output results , then , The string " One hundred and twenty ginseng " Convert to int type , And see how it works .

## programme

First , Use Integer Of parseInt Method , The string "123" Convert to int type , Normal operation and output int Type value 123; then , Again using Integer Of parseInt Method , The string " One hundred and twenty ginseng " Convert to int type , After operation , There will be anomalies .

## step

To implement this case, follow the steps below .

## Step one ： Build test methods

stay day02 New class under package TestInteger, Add test methods to this class testParseInt, The code is as follows ：

`````` package day02;

import org.junit.Test;

public class TestInteger{
/**
* test Integer Of parseInt Method
*/
@Test
public void testParseInt(){

}
}``````

## Step two ： The string "123" Convert to integer type

Use Integer Of parseInt Method , The string "123" Convert to int type , Normal operation and output int Type value 123, The code is as follows ：

`````` package day02;

import org.junit.Test;

public class TestInteger{
/**
* test Integer Of parseInt Method
*/
@Test
public void testParseInt(){

String str="123";
int value=Integer.parseInt(str);
System.out.println(value);//123
}
}``````

Run the above code , The console output is ：

`    123`

It indicates that the string "123" Convert to int Type of 123.

## Step three ： character string " One hundred and twenty ginseng " Convert to int type

Again using Integer Of parseInt Method , The string " One hundred and twenty ginseng " Convert to int type , The code is as follows ：

`````` package day02;

import org.junit.Test;

public class TestInteger{
/**
* test Integer Of parseInt Method
*/
@Test
public void testParseInt(){

String str="123";
int value=Integer.parseInt(str);
System.out.println(value);//123

str=" One hundred and twenty ginseng ";
// Will throw out NumberFormatException
value=Integer.parseInt(str);
}
}``````

After running the above code , There will be anomalies ：

``java.lang.NumberFormatException:For input string:" One hundred and twenty ginseng "``

It can be seen from the abnormal situation that ,Java The program could not string " One hundred and twenty ginseng " Convert to int type , therefore , Throw out java.lang.NumberFormatException abnormal . So it's using Integer Of parseInt When the method is used , Note that the parameters of the passed in method are numbers .