Android APIs
Added in API level 1
package

java.lang

Interfaces

Appendable Declares methods to append characters or character sequences. 
AutoCloseable Defines an interface for classes that can (or need to) be closed once they are not used any longer. 
CharSequence This interface represents an ordered set of characters and defines the methods to probe them. 
Cloneable This (empty) interface must be implemented by all classes that wish to support cloning. 
Comparable<T> This interface should be implemented by all classes that wish to define a natural order of their instances. 
Iterable<T> Instances of classes that implement this interface can be used with the enhanced for loop. 
Readable Represents a sequence of characters that can be incrementally read (copied) into a CharBuffer
Runnable Represents a command that can be executed. 
Thread.UncaughtExceptionHandler Implemented by objects that want to handle cases where a thread is being terminated by an uncaught exception. 

Classes

Boolean The wrapper for the primitive type boolean
Byte The wrapper for the primitive type byte
Character The wrapper for the primitive type char
Character.Subset  
Character.UnicodeBlock Represents a block of Unicode characters. 
Class<T> The in-memory representation of a Java class. 
ClassLoader Loads classes and resources from a repository. 
Compiler Does nothing on Android. 
Double The wrapper for the primitive type double
Enum<E extends Enum<E>> The superclass of all enumerated types. 
Float The wrapper for the primitive type float
InheritableThreadLocal<T> A thread-local variable whose value is passed from parent to child thread. 
Integer The wrapper for the primitive type int
Long The wrapper for the primitive type long
Math Class Math provides basic math constants and operations such as trigonometric functions, hyperbolic functions, exponential, logarithms, etc. 
Number The abstract superclass of the classes which represent numeric base types (that is Byte, Short, Integer, Long, Float, and Double
Object The root class of the Java class hierarchy. 
Package Contains information about a Java package. 
Process Represents an external process. 
ProcessBuilder Creates operating system processes. 
Runtime Allows Java applications to interface with the environment in which they are running. 
RuntimePermission Legacy security code; do not use. 
SecurityManager Legacy security code; do not use. 
Short The wrapper for the primitive type short
StackTraceElement A representation of a single stack frame. 
StrictMath Class StrictMath provides basic math constants and operations such as trigonometric functions, hyperbolic functions, exponential, logarithms, etc. 
String An immutable sequence of characters/code units (chars). 
StringBuffer A modifiable sequence of characters for use in creating strings, where all accesses are synchronized. 
StringBuilder A modifiable sequence of characters for use in creating strings. 
System Provides access to system-related information and resources including standard input and output. 
Thread A Thread is a concurrent unit of execution. 
ThreadGroup ThreadGroup is a means of organizing threads into a hierarchical structure. 
ThreadLocal<T> Implements a thread-local storage, that is, a variable for which each thread has its own value. 
Throwable The superclass of all classes which can be thrown by the VM. 
Void Placeholder class for the Java keyword void

Enums

Thread.State A representation of a thread's state. 

Exceptions

ArithmeticException Thrown when the an invalid arithmetic operation is attempted. 
ArrayIndexOutOfBoundsException Thrown when the an array is indexed with a value less than zero, or greater than or equal to the size of the array. 
ArrayStoreException Thrown when a program attempts to store an element of an incompatible type in an array. 
ClassCastException Thrown when a program attempts to cast a an object to a type with which it is not compatible. 
ClassNotFoundException Thrown when a class loader is unable to find a class. 
CloneNotSupportedException Thrown when a program attempts to clone an object which does not support the Cloneable interface. 
EnumConstantNotPresentException Thrown if an enum constant does not exist for a particular name. 
Exception Exception is the superclass of all classes that represent recoverable exceptions. 
IllegalAccessException Thrown when a program attempts to access a field or method which is not accessible from the location where the reference is made. 
IllegalArgumentException Thrown when a method is invoked with an argument which it can not reasonably deal with. 
IllegalMonitorStateException Thrown when a monitor operation is attempted when the monitor is not in the correct state, for example when a thread attempts to exit a monitor which it does not own. 
IllegalStateException Thrown when an action is attempted at a time when the VM is not in the correct state. 
IllegalThreadStateException Thrown when an operation is attempted which is not possible given the state that the executing thread is in. 
IndexOutOfBoundsException Thrown when a program attempts to access a value in an indexable collection using a value which is outside of the range of valid indices. 
InstantiationException Thrown when a program attempts to access a constructor which is not accessible from the location where the reference is made. 
InterruptedException Thrown when a waiting thread is activated before the condition it was waiting for has been satisfied. 
NegativeArraySizeException Thrown when an attempt is made to create an array with a size of less than zero. 
NoSuchFieldException Thrown when the VM notices that a program tries to reference, on a class or object, a field that does not exist. 
NoSuchMethodException Thrown when the VM notices that a program tries to reference, on a class or object, a method that does not exist. 
NullPointerException Thrown when a program tries to access a field or method of an object or an element of an array when there is no instance or array to use, that is if the object or array points to null
NumberFormatException Thrown when an invalid value is passed to a string-to-number conversion method. 
ReflectiveOperationException Superclass of exceptions related to reflection. 
RuntimeException RuntimeException is the superclass of all classes that represent exceptional conditions which occur as a result of executing an application in the VM. 
SecurityException Thrown when a security manager check fails. 
StringIndexOutOfBoundsException Thrown when the a string is indexed with a value less than zero, or greater than or equal to the size of the array. 
TypeNotPresentException Thrown when a program tries to access a class, interface, enum or annotation type through a string that contains the type's name and the type cannot be found. 
UnsupportedOperationException Thrown when an unsupported operation is attempted. 

Errors

AbstractMethodError Thrown by the VM when an abstract method is called. 
AssertionError Thrown when an assertion has failed. 
ClassCircularityError Thrown when the VM notices that an attempt is made to load a class which would directly or indirectly inherit from one of its subclasses. 
ClassFormatError Thrown by a class loader when a class file has an illegal format or if the data that it contains can not be interpreted as a class. 
Error Error is the superclass of all classes that represent unrecoverable errors. 
ExceptionInInitializerError Thrown when an exception occurs during class initialization. 
IllegalAccessError Thrown when the VM notices that a program tries access a field which is not accessible from where it is referenced. 
IncompatibleClassChangeError IncompatibleClassChangeError is the superclass of all classes which represent errors that occur when inconsistent class files are loaded into the same running image. 
InstantiationError Thrown when the VM notices that a program tries to create a new instance of a class which has no visible constructors from the location where new is invoked. 
InternalError Thrown when the VM notices that it has gotten into an undefined state. 
LinkageError LinkageError is the superclass of all error classes that occur when loading and linking class files. 
NoClassDefFoundError Thrown when the VM is unable to locate a class which it has been asked to load. 
NoSuchFieldError Thrown when the VM notices that a program tries to reference, on a class or object, a field that does not exist. 
NoSuchMethodError Thrown when the VM notices that a program tries to reference, on a class or object, a method that does not exist. 
OutOfMemoryError Thrown when a request for memory is made that can not be satisfied using the available platform resources. 
StackOverflowError Thrown when the depth of the stack of the running program exceeds some platform or VM specific limit. 
ThreadDeath ThreadDeath is thrown when a thread stops executing. 
UnknownError Thrown when the VM must throw an error which does not match any known exceptional condition. 
UnsatisfiedLinkError Thrown when an attempt is made to invoke a native for which an implementation could not be found. 
UnsupportedClassVersionError Thrown when an attempt is made to load a class with a format version that is not supported by the VM. 
VerifyError Thrown when the VM notices that an attempt is made to load a class which does not pass the class verification phase. 
VirtualMachineError VirtualMachineError is the superclass of all error classes that occur during the operation of the VM.