How to create or initialize Generic Type Array

solution 1

Limitation: It's not work if input array is null.

public static <T> T[] subarray(T[] array, int startIndexInclusive, int endIndexExclusive) {
        if (array == null) {
            return null;
        }

        if (startIndexInclusive < 0) {
            startIndexInclusive = 0;
        }
        if (endIndexExclusive > array.length) {
            endIndexExclusive = array.length;
        }

        Class<?> type = array.getClass().getComponentType();
        int newSize = endIndexExclusive - startIndexInclusive;
        if (newSize < 0) {
            final T[] emptyArray = (T[]) Array.newInstance(type, 0);
            return emptyArray;
        }

        T[] subarray = (T[]) Array.newInstance(type, newSize);
        System.arraycopy(array, startIndexInclusive, subarray, 0, newSize);
        return subarray;
    }

solution 2

It's work if input array is null. But it's more verbose for invoking.

public static <T> T[] subarray(T[] array, int startIndexInclusive, int endIndexExclusive, Class<T>> clazz) {
     T[] emptyArray = (T[]) Array.newInstance(clazz, 0);

        if (array == null) {
            return emptyArray;
        }

        if (startIndexInclusive < 0) {
            startIndexInclusive = 0;
        }
        if (endIndexExclusive > array.length) {
            endIndexExclusive = array.length;
        }

        if (newSize < 0) {
            return emptyArray;
        }

        T[] subarray = (T[]) Array.newInstance(clazz, newSize);
        System.arraycopy(array, startIndexInclusive, subarray, 0, newSize);
        return subarray;
    }

Java Swing JTextField: Number only and give length

Solution 1

Simple but It can't work for "CTRL + V" scenario

private class NumberOnlyAdapter extends KeyAdapter {

        private final int maxLength;

        private NumberOnlyAdapter(int maxLength) {
            this.maxLength = maxLength;
        }

        @Override
        public void keyTyped(KeyEvent e) {
            char typed = e.getKeyChar();
            CharMatcher notDigit = noneOf("0123456789").and(isNot((char) VK_BACK_SPACE)).and(isNot((char) VK_DELETE));
            JTextField textField = (JTextField) e.getComponent();
            if (notDigit.apply(typed) || textField.getText().length() >= maxLength) {
                e.consume();
            }
        }

    }

...
int maxLength = 8;
JTextField textField = new JTextField();
textField.addKeyListener(new NumberOnlyAdapter(maxLength));

Solution 2

It's work for all conditions

import static org.apache.commons.lang3.StringUtils.*;

import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;

public class NumericOnlyAndMaxLengthFilter extends DocumentFilter {
    private int maxLength = 0;


    public NumericOnlyAndMaxLengthFilter() {
       // allow any length of numeric
    }

    public NumericOnlyAndMaxLengthFilter(int maxLength) {
        this.maxLength = maxLength;
    }

    @Override
    public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
        if (isNumeric(string)) {
            if (isExceedMaxLength(fb, string)) {
                return;
            }
            super.insertString(fb, offset, string, attr);
        }
    }

    @Override
    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
        if (isNumeric(text)) {
            if (isExceedMaxLength(fb, text)) {
                return;
            }
            super.insertString(fb, offset, text, attrs);
        }
    }

    private boolean isExceedMaxLength(FilterBypass fb, String text) {
        return maxLength > 0 && (fb.getDocument().getLength() + text.length()) > maxLength;
    }
}

...
int maxLength = 8;
JTextField textField = new JTextField();
((AbstractDocument)textField .getDocument()).setDocumentFilter(new NumericOnlyAndMaxLengthFilter(maxLength));

Maven generate HTML Junit report

• add to pom.xml

    org.apache.maven.plugins
    maven-surefire-plugin
    
        true
    



    org.jvnet.maven-antrun-extended-plugin
    maven-antrun-extended-plugin
    
        
            test-reports
            test
            
                
                    
                        
                            
                        
                        
                    
                
            
            
                run
            
        
    
    
        
            org.apache.ant
            ant-junit
            1.8.4
        
        
            org.apache.ant
            ant-trax
            1.8.0
        
    

• Don't bind the AntRun plugin to the test phase, move the configuration outside the execution and call mvn antrun:run on the command line to generate the reports when wanted.
• Or use the testFailureIgnore option of the test mojo and set it to true in the surefire plugin
• Use maven command arguments

$mvn test -Dmaven.test.failure.ignore=true

Java - better performance String formatter

/**
     * Substitutes each {@code %s} in {@code template} with an argument. These
     * are matched by position - the first {@code %s} gets {@code args[0]}, etc.
     * If there are more arguments than placeholders, the unmatched arguments will
     * be appended to the end of the formatted message in square braces.
     *
     * @param template a non-null string containing 0 or more {@code %s}
     *     placeholders.
     * @param args the arguments to be substituted into the message
     *     template. Arguments are converted to strings using
     *     {@link String#valueOf(Object)}. Arguments can be null.
     */
    public static String format(String template, Object... args) {
        template = String.valueOf(template); // null -> "null"
        // start substituting the arguments into the '%s' placeholders
        StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
        int templateStart = 0;
        int i = 0;
        while (i < args.length) {
            int placeholderStart = template.indexOf("%s", templateStart);
            if (placeholderStart == -1) {
                break;
            }
            builder.append(template.substring(templateStart, placeholderStart));
            builder.append(args[i++]);
            templateStart = placeholderStart + 2;
        }
        builder.append(template.substring(templateStart));

        // if we run out of placeholders, append the extra args in square braces
        if (i < args.length) {
            builder.append(" [");
            builder.append(args[i++]);
            while (i < args.length) {
                builder.append(", ");
                builder.append(args[i++]);
            }
            builder.append(']');
        }

        return builder.toString();
    }

   public static void main(String[] args) {
        Stopwatch stopwatch = new Stopwatch();
        stopwatch.start();
        String result = Formatter.format("My name is: %s. I was start from: %s. ", "Sean", "25/05/2012", "another value here");
        stopwatch.stop();
        System.out.println(stopwatch.elapsedTime(TimeUnit.NANOSECONDS));
        System.out.println(result);
        stopwatch.reset();
        stopwatch.start();
        result = String.format("My name is: %s. I was start from: %s.", "Sean", "25/05/2012", "another value here");
        stopwatch.stop();
        System.out.println(stopwatch.elapsedTime(TimeUnit.NANOSECONDS));
        System.out.println(result);
    }