Unsupported major.minor version 52.0 in java

Exception in thread "main" java.lang.UnsupportedClassVersionError: client : 
Unsupported major.minor version 52.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

Unsupported major.minor version is a Java version mismatch error you get when you compile and run your applications on two different versions or java (example java 7 and java 8)

1. Go to Eclipse -> Preferences
2. Go to Java -> Installed JRE (say its JAVA SE 8)
3. Now Right Click on your Project directory -> Properties
4. Go to Java Build Path -> Libraries
5. Here too the JRE must be the same (say JAVA SE 8), if not change it.