This keyword in Java: this. Member variable, operator, common modifier, shift operator, common shortcut keys in eclipse

0. this keyword in Java

0.0. After the initial object-oriented idea, when we come into contact with classes and objects, we will inevitably come into contact with the this keyword

0.1. this keyword refers to a reference to the current object.

0.2 function of this

0.2.1. this. Attribute name

The meaning of this writing is to distinguish the problem of duplicate names of member variables (non static variables in the class) and local variables passed in the method (construction method, value passing method setValue())

We know that class variables (static variables) do not depend on classes. Class variables (static variables) are loaded first

When the class is loaded later, the methods in the class are used to construct the formal parameters in the method. Is in order of priority.

That is, when the name of this. Member variable is not added,

  For example:        public void setTestint(int testint) {
        testint = testint;
    } // He passed the formal parameter variable to himself, and the last member variable was not assigned


Execute the following code:

package bilibili.bobro.operator.test;

public class ThisTest 

	public static void main(String[] args) 
		Test t=new Test();



class Test
	private int testint;
	private boolean testboo;
	private String teststr;
	private double testdou;
	private char testchar;
	public int getTestint() {
		return testint;
	public void setTestint(int testint) {
		testint = testint;
	public boolean isTestboo() {
		return testboo;
	public void setTestboo(boolean testboo) {
		testboo = testboo;
	public String getTeststr() {
		return teststr;
	public void setTeststr(String teststr) {
		teststr = teststr;
	public double getTestdou() {
		return testdou;
	public void setTestdou(double testdou) {
		testdou = testdou;
	public char getTestchar() {
		return testchar;
	public void setTestchar(char testchar) {
		testchar = testchar;

The console output results are as follows:

  If you don't add this, then

setVal (formal parameter)


         Formal parameter (local variable) = formal parameter (local variable)


Pass the argument to the formal parameter in the method, and then the formal parameter assigns its own value. The member variables in the class are not involved at all.

The arguments passed in didn't touch, so they were still empty.

Local variable: in the method definition or on the method declaration.  

Local variable: in memory stack.

Local variable: exists with the method call and disappears with the method call.  

If you don't add this, the local variable of others will backhand and pass it to themselves. After passing it, it will disappear and log off the memory on the memory stack.

I've been in a hundred flowers and leaves don't touch me. Your member variable SET method didn't get any value.


Just soy sauce purple~~~~

So this is very important~~


1. Operators and, or, XOR

&: bitwise AND

|: bitwise OR

^: bitwise XOR (the key lies in XOR. 0 is returned for the same, and or is performed for different)


   0000 1111   11 00

^ 1111  0000  11 00

   1111  1111   00 00


& 0110



|   1010


2. Modifier private   public, default (default/friendly), protected

private   Only available within the current class.

default: friend   Same kind, same package available   Parent child grandchildren not available

Public: public class

protected: protect yourself, friends and grandchildren?

3. Shift operator "> >   and   " << "

Take 11 as an example:    

Binary of 11:                     0000 1011     eleven

11>>1                               0000 0101    5

11>>2                              0000 0010     2

11<<1                              0001 0110     22       

11<<2                              0010 1100     44            

Moving right is equivalent to division, but we don't say division, because moving left and right turns into binary, and then moves left and right to supplement 0

In a computer, the speed of bit operation is greater than * / (multiplication and division)


3. Shortcut keys in eclipse:

Mastering the code compiler will help us improve ourselves faster:

In eclipse

Quickly generate ste and get methods. CTRL+SHIFT+S

Quickly copy the previous line: ctrl+Alt+down/up


Tags: Java Eclipse Back-end

Posted on Sat, 30 Oct 2021 15:59:49 -0400 by petroz