Java Performance

This post is about performance factors in java. There are many performance factors in java. Here i am mentioning some of the performance factors which i have used in early days in java. I will keep posted some approach, experience on performance improvement.

some of the performance tips are,

1. ArrayList is faster than Vector except when there is no lock acquisition required.
2. Use StringBuffer in place of String if you are doing lots of string manipulation it will reduce memory by avoiding creating lots of string garbage. If you are using java5 then consider StringBuilder but that is not synchronized so beware.
3. Try to make variable , class , method final whenever possible that’s allow compiler to do lots of optimization e.g. compile time binding so you will get faster output.
4. Static methods are bonded compile time while non static methods are resolved at runtime based on object type so static method will be faster than non static.
5. Don't call methods in for loop for checking condition e.g. length() size() etc. instead of doing this , use modified version.
6. Use exceptions only where you really need them
7. Local variables are the faster than instance variables, which are in turn faster than array elements
8. Use the fastest available JVM
9. '==' is faster than equals()
10. Creating Doubles from strings is slow
11. Combine similar loops
12. Don't create too may objects
13. Beware of object leaks (references to objects that are never nulled)
14. Use Lazy loading to avoid unnecessary pre-loading of child data
15. Do bulk updates to reduce database calls
16. Use the print() method rather than the println() method

Difference between JDK, JRE and JVM

Understanding the difference between JDK, JRE and JVM is important in Java. We are using JDK, JRE and JVM daily, but many of us not knowing the difference of them. Let we discuss the difference between JDK, JRE and JVM.

JVM

JVM is the short form of Java Virtual Machine. It is a specification that provides runtime environment to execute the java bytecode. JVM is platform dependent because configuration of each OS is differ. But we know that, java is platform independent because java bytecode can be executed in any platform.

JRE

JRE is the short form for Java Runtime Environment. JRE is providing the runtime environment. JRE is the implementation of JVM. It physically exist. It contains set of libraries and set of files that JVM uses at runtime.

JDK

JDK is the short form of Java Development Kit. It physically exist. It contains JRE and Development tools.

Program - FLAMES

I have written FLAMES program around 6 years back when i was started to learn Java programming.
Initially i have written in 'C' language and later the same logic to be used in java program with JFrame for GUI. This program seems to be very easy for those who are having good understanding and basic knowledge in java, but i was struggled to find out this logic when was started this in 'C' language.

I found an issue in this program just before posting this code. Can you please trace and find out the issue?


Try below and find the relationship with your loved one

Name 1:
Name 2:

import java.awt.Color;
import java.awt.Font;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.UIManager;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class Flames extends JFrame implements ActionListener{
JLabel lbl1 = new JLabel("Name 1");
JLabel lbl2 = new JLabel("Name 2");
JTextField fld1 = new JTextField();
JTextField fld2 = new JTextField();;
JButton btn = new JButton("Submit");
JLabel rlt = new JLabel("");
public Flames()  throws Throwable{
super("Flames");
setLayout(null);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setBackground(Color.LIGHT_GRAY);
setBounds(100, 100, 300, 300);
lbl1.setBounds(50, 40, 100, 40);
lbl2.setBounds(50, 100, 100, 40);
fld1.setBounds(120, 40, 150, 30);
fld2.setBounds(120, 100, 150, 30);
btn.setBounds(110,150,100,30);
rlt.setBounds(110,200,100,30);
rlt.setFont(new Font("Courier New", Font.BOLD, 18));
rlt.setForeground(Color.RED);
add(btn);
add(lbl1);
add(lbl2);
add(fld1);
add(fld2);
add(rlt);
btn.addActionListener(this);
}
  public static void main(String args[])  throws Throwable {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
new Flames();
  }
  public void actionPerformed(ActionEvent e) {
rlt.setText("");
String name1 = fld1.getText().toUpperCase();
String name2 = fld2.getText().toUpperCase();
if(name1 ==null || name1.equals("")) {
JOptionPane.showMessageDialog(null, "Name 1 must not be empty.", "Error", JOptionPane.ERROR_MESSAGE);
} else if(name2 ==null || name2.equals("")) {
JOptionPane.showMessageDialog(null, "Name 2 must not be empty.", "Error", JOptionPane.ERROR_MESSAGE);
} else if(name1.equals(name2)) {
JOptionPane.showMessageDialog(null, "Name 1 and Name 2 must not be same.", "Error", JOptionPane.ERROR_MESSAGE);
} else {
rlt.setText(getFlames(name1, name2));
}
  }
  public String getFlames(String name1, String name2)  {
    String result = "";
    char[] f = { 'F', 'L', 'A', 'M', 'E', 'S' };
    char[] n1 = name1.toCharArray();
    char[] n2 = name2.toCharArray();
    int len = 0;
    for (int i = 0; i < n1.length; i++) {
      for (int j = 0; j < n2.length; j++) {
        if (n1[i] == n2[j])  {
          n1[i] = '0';
          n2[j] = '0';
          break;
        }
      }
    }
    for (int i = 0; i < n1.length; i++) {
      if (n1[i] != '0') {
        len++;
      }
    }
    for (int i = 0; i < n2.length; i++) {
      if (n2[i] != '0') {
        len++;
      }
    }
    int k = 1;int l = 0;int c = 1;
    for (;;)  {
      if (k == len)  {
        if (f[l] != '0')  {
          f[l] = '0';
          k = 1;
          l++;
          c++;
          if (l >= 6) {
            l = 0;
          }
          if (c == 6) {
            break;
          }
        } else {
          l++;
          if (l >= 6) {
            l = 0;
          }
        }
      } else  {
        if (f[l] != '0') {
          k++;
        }
        l++;
        if (l >= 6) {
          l = 0;
        }
      }
    }
    for (int i = 0; i < f.length; i++) {
      if (f[i] != '0') {
        if (f[i] == 'F') {
          result = "FRIEND";
        } else if (f[i] == 'L') {
          result = "LOVE";
        } else if (f[i] == 'A') {
          result = "AFFECTION";
        } else if (f[i] == 'M') {
          result = "MARRIAGE";
        } else if (f[i] == 'E') {
          result = "ENEMY";
        } else if (f[i] == 'S') {
          result = "SISTER";
        }
      }
    }
    return result;
  }
}