Using Kate

Kate is an easy-to-use WYSIWYG text editor that has many features useful for programming.
When the editor starts, you may see a window displaying a tip. Click the Close button.
The window may be too small. Click the Maximize button to make the editor full screen.

Kate has a title bar that displays the name of the current document, a menu bar, and a standard toolbar of buttons.
The buttons from left to right are New, Open, Back, Forward, Save, Save As, Stop, Undo, Redo, Cut, Copy, Paste, Find, Increase/Decrease Font Size, Split Vertically, Split Horizontally, Close Current, Print.
The left column lists all of the open files (file list), or allows you to find and open a file (selector).
To switch between the file list and the selector, click the tab above the column.
The bottom window contains a shell prompt.
If you do not see a shell prompt, click Settings, Tool Views, Show Terminal.
The top window allows you to type and edit text.
To increase the size of the editor window, move to the bottom until you see double arrows and drag downwards.

If the text is difficult to read, you can change the font as follows:
Click Settings, Configure Kate.
Click Editor and click Fonts.
Scroll down to Courier 10 Pitch. (Courier is a monospace font that is useful for programming.)
Select a larger size, e.g. 14.

If you save your file with a .java extension, the Java code will be colour-coded.
Objects are blue, keywords are black and bold, comments are grey and italic, data types are brown, string literals are red, characters are pink, etc.
To view a description of highlights, click Settings, Configure Kate, Editor, Highlighting.
To put the editor into Java mode immediately (before saving), click Tools, Highlight Mode, Sources, Java.

To indent you can either use spaces or tabs. By default, the tab key indents 8 spaces.
To change the number of spaces a tab indents, click Settings, Configure Kate.
Click Editor, click Editing, and change "Tab and indent width" to 3.
This will only change how it appears in the editor, since tab characters are stored in the file.
If you want the tab key to insert 3 spaces, check "Replace tabs with spaces."

Avoid using the mouse because it slows you down. Many common keyboard shortcuts work in a number of programs including Kate.

Use Ctrl-S to save, Ctrl-O to open, and Ctrl-N for a new file.
Use Ctrl-X to cut, Ctrl-C to copy, Ctrl-V to paste.
Use Ctrl-Z to undo, Ctrl-Y to redo.
Use the arrow keys, Home, End, Page Up and Page Down to move the cursor.
Use Shift while moving the cursor to select text, or press Ctrl-A to select all text.

Press the up and down arrow keys to cycle through recently used shell commands.
Edit a previous command using Home, End, Backspace, Delete and left and right arrow keys.
Press the Tab key to complete the name of a file so you do not have to type the full name.