IntelliJ IDEA

Basic code completion (Ctrl Space) finalizes a class, method, variable name, and Java keywords, plus commonly used names for fields and variables depending on their type. It can be automatically invoked, popping up the available methods and fields list.

The SmartType code completion (Ctrl Shift Space) filters the method and variable list to match the expected expression type. It works at the right-hand side of assignments, in variable initializers, return statements and anywhere else where IntelliJ IDEA can guess the expected type.

The Class Name (Ctrl Alt Space) Java code completion finishes a Java class name anywhere in the project or libraries independently of imports in the current file.

All types of Java code completion support "CamelHumps", so you can enter only the capitalized letters in case of long and complex method or field names (e.g. "aAL" instead of addActionListner).

When coding a new method call, a tooltip showing the target method signature pops up after you type the opening "(" character or invoke code completion features. The parameter highlighted in bold is the one on which the caret is currently positioned. You can control the popup interval or disable the popup completely in Completion settings.

For existing calls, press Ctrl P anywhere inside a method call to pop up the target method's signature. Again, the parameter shown in bold is the one on which the caret is currently positioned. When the popup is shown, you can use the Tab key for quick navigation between parameters in the code.

Import Assistant helps to automatically insert import statements while typing code, and detects non-imported classes found in pasted blocks of code. When you use the name of a Java class from anywhere in a project library, but the class has not been imported into the current file, a hint with the suggestion to import the class pops up over the text. Pressing Alt Enter inserts the import statement. Moreover, when you copy a block of text from one file and paste it into another, IntelliJ IDEA automatically detects all the classes that are used inside the copied block but have not been imported to the destination file. It then shows a list of all such classes and allows you to select classes you want to import into the new file.

Import optimizer (Ctrl Alt O) allows users to quickly manage imports in a file or set of files: remove unused imports, reorder, and clarify them. There is also a flexible set of options to match your preferences for setting the layout of import statements.

Having positioned the caret at a class, file or directory (in any of the project views) you only need to press a shortcut Ctrl Shift C to store the full path to the selected element in the clipboard for future use both inside and outside IntelliJ IDEA.

You can copy a reference to any Java symbol into the clipboard, with a single keystroke. Position the caret at a symbol in the editor or one of the project views and press Ctrl Alt Shift C. When you later paste the copied value, it will be inserted with proper reference resolution with regard to the current context.