Learn to use the idea breakpoint debugging tool

IDEA Breakpoint debugging

In the process of breakpoint debugging, it is always running , After setting a breakpoint on a line, it will stop here . So as to find the problem . Be commonly called Debug

Breakpoint debugging shortcut

• F7（ Jump into method ）
• F8（ skip — Step through the code ）
• shift+F8（ Jump out of the way ）
• F9（ Step through the code Resume）

Breakpoint debugging case

Case 1 is executed circularly

package com.dzu.cn;

/** * @Author ChenRuXu * @Date 2022/2/14 22:23 * @Version 1.0 */
public class Debug01 {
    
    public static void main(String[] args) {
    
        // Demonstrate line by line execution 
        int sum=0;
        for (int i=0;i<5;i++){
    
            sum+=i;
            System.out.println("i="+i);
            System.out.println("sum="+sum);
        }
        System.out.println(" sign out for");
    }
}

Click the left mouse button on the desired line and then perform breakpoint debugging .

After performing breakpoint debugging, the following page appears
Be careful ：F9 Resume You can dynamically add breakpoints, which still take effect during execution

F8 step over Skip step by step

F7 step into Jump into method

force step into Force into the method body


here F7 We can see clearly the execution process of the program and the changes of variables .

Case 2 ： Array out of bounds execution exception

package com.dzu.cn;

/** * @Author ChenRuXu * @Date 2022/2/14 22:48 * @Version 1.0 */
public class Debug02 {
    
    public static void main(String[] args) {
    
       int[] arr ={
    1,10,-1};
        for (int i = 0; i <=arr.length ; i++) {
    
            System.out.println(arr[i]);
        }
        System.out.println(" sign out for loop ");
    }
}

Case 3 tracking source code

Observe Arrays.sort(arr) How it's sorted

package com.dzu.cn;

import java.util.Arrays;

/** * @Author ChenRuXu * @Date 2022/2/14 22:56 * @Version 1.0 */
public class Dubug03 {
    
    public static void main(String[] args) {
    
        int arr[] ={
    1,-1,10,-20,100};
        Arrays.sort(arr);
        for ( int i= 0;i<arr.length;i++){
    
            System.out.print(arr[i]+"\t");
        }
    }
}

Learn to use breakpoints in debugging F7 Jump into the method body

Use F7 Later, we found that it did not enter the source code . Here is our solution .

Method 1 ：force step into Use enforcement to enter

Method 2 adopts configuration method to realize

Find the option of breakpoint debugging in the settings .

Will be one of the java.* ,javax.* Uncheck the .

By default, it is not allowed to enter the source code

At this point we can use dubug To enter the source code debugging .

On this basis, if we are using F7 Will continue to enter .

This is where we really implement the sorting method （ Double quick row ）

After entering the final source code , reflection How to exit to the main method

Jump out of the previous method first We need to use shift+F8（ Jump out of the way ） Jump to the place where the call is sorted and step back to the main method

Case four ：F9 resume And dynamic breakpoints

idea Support dynamic breakpoints during the running process

package com.dzu.cn;

import java.util.Arrays;

/** * @Author ChenRuXu * @Date 2022/2/14 22:56 * @Version 1.0 */
public class Dubug03 {
    
    public static void main(String[] args) {
    
        int arr[] ={
    1,-1,10,-20,100};
        Arrays.sort(arr);
        for ( int i= 0;i<arr.length;i++){
    
            System.out.print(arr[i]+"\t");
        }

        System.out.println(1);
        System.out.println(2);
        System.out.println(3);
        System.out.println(4);

    }
}

Use F9 It will go directly to the position of the second breakpoint . Then we dynamically add a breakpoint .

Now click F9 It will go to the position where the breakpoint is dynamically added

summary

Debugging with breakpoints is , When we analyze the source code for troubleshooting and learning in the future, it is one of the essential contents .