# Java editor

## Toolbar actions

Toolbar Button | Command | Description
--- | --- | ---
| Toggle Java Editor Breadcrumb | This button enables the Java editor breadcrumb. The enablement is remembered for each perspective separately.
| Toggle Mark Occurrences | Turns mark occurrences on and off in the Java editor.
| Toggle Block Selection Mode | This button enables block (aka column) selection mode in the editor.
| Show Whitespace Characters | This button enables the display of whitespace characters in an editor.

Show Source of Selected Element Only

This button enabled display of a segmented view of the source of a compilation unit.

This button is only shown if you customize your perspective to show the Editor Presentation actions.

For example, if a method is selected in the Outline view, the Show Source Of Selected Element Only option causes only that method to be displayed in the editor, as opposed to the entire class.

Off: The entire compilation unit is displayed in the editor, with the selected Java element highlighted in the marker bar with a range indicator.

On: Only the selected Java element is displayed in the editor, which is linked to the selection in the Outline or Type Hierarchy view.

| Go to Next Problem | This command navigates to the next problem marker in the active editor.
| Go to Previous Problem | This command navigates to the previous problem marker in the active editor.

## Key binding actions

The following actions can only be reached through key bindings. The Key bindings field in Window > Preferences > General > Keys must be set to 'Emacs'.

Key binding | Description
--- | ---
`Alt`+`0` `Ctrl`+`K`, `Esc` `0` `Ctrl`+`K` | Deletes from the cursor position to the beginning of the line.
`Ctrl`+`K` | Deletes from the cursor position to the end of the line.
`Ctrl`+`Space`, `Ctrl`+`2` | Sets a mark at the current cursor position.
`Ctrl`+`X` `Ctrl`+`X` | Swaps the cursor and mark position if any.

Java editor

Opening an editor for a selected element

Java outline
Java editor preferences
JDT actions
Views and editors