openjdk 1.7 in eclipse: operator is not allowed for source level below 1.7
In your project's preferences, you must set the compiler --source option to 1.7 and --target option to 1.7 also. There are dedicated option boxes for that.
Right-click on the project. Choose Properties. Choose Java Compiler on the left. Choose 1.7 for the Compiler Compliance level. If the 2 drop-downs below that aren't 1.7, uncheck Use default compliance settings and set those to 1.7.
right click on the error, choose quick fix, and select change JRE to 1.7
If you want to use below version, use
Map<String, Integer> map = new HashMap<String, Integer>();instead of
HashMap<String, Integer> map = new HashMap<>();