Java – How to make a list with checkboxes in Java Swing

javajcheckboxswing

What would be the best way to have a list of items with a checkbox each in Java Swing?

I.e. a JList with items that have some text and a checkbox each?

Best Answer

A wonderful answer is this CheckBoxList. It implements Telcontar's answer (though 3 years before :)... I'm using it in Java 1.6 with no problems. I've also added an addCheckbox method like this (surely could be shorter, haven't used Java in a while):

public void addCheckbox(JCheckBox checkBox) {
    ListModel currentList = this.getModel();
    JCheckBox[] newList = new JCheckBox[currentList.getSize() + 1];
    for (int i = 0; i < currentList.getSize(); i++) {
        newList[i] = (JCheckBox) currentList.getElementAt(i);
    }
    newList[newList.length - 1] = checkBox;
    setListData(newList);
}

I tried out the demo for the Jidesoft stuff, playing with the CheckBoxList I encountered some problems (behaviors that didn't work). I'll modify this answer if I find problems with the CheckBoxList I linked to.

Related Solutions

Java – How to efficiently iterate over each entry in a Java Map

Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

On Java 10+:

for (var entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

Java – How to round a number to n decimal places in Java

Use setRoundingMode, set the RoundingMode explicitly to handle your issue with the half-even round, then use the format pattern for your required output.

Example:

DecimalFormat df = new DecimalFormat("#.####");
df.setRoundingMode(RoundingMode.CEILING);
for (Number n : Arrays.asList(12, 123.12345, 0.23, 0.1, 2341234.212431324)) {
    Double d = n.doubleValue();
    System.out.println(df.format(d));
}

gives the output:

12
123.1235
0.23
0.1
2341234.2125

EDIT: The original answer does not address the accuracy of the double values. That is fine if you don't care much whether it rounds up or down. But if you want accurate rounding, then you need to take the expected accuracy of the values into account. Floating point values have a binary representation internally. That means that a value like 2.7735 does not actually have that exact value internally. It can be slightly larger or slightly smaller. If the internal value is slightly smaller, then it will not round up to 2.7740. To remedy that situation, you need to be aware of the accuracy of the values that you are working with, and add or subtract that value before rounding. For example, when you know that your values are accurate up to 6 digits, then to round half-way values up, add that accuracy to the value:

Double d = n.doubleValue() + 1e-6;

To round down, subtract the accuracy.

Best Answer

Related Solutions

Java – How to efficiently iterate over each entry in a Java Map

Java – How to round a number to n decimal places in Java

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